CN115191042A - Electrode composition, electrode sheet for all-solid-state secondary battery, and method for producing electrode sheet for all-solid-state secondary battery and all-solid-state secondary battery - Google Patents

Abstract

The present invention provides an electrode composition, an electrode sheet for an all-solid-state secondary battery and an all-solid-state secondary battery using the electrode composition, and an electrode sheet for an all-solid-state secondary battery and a manufacturing method for the all-solid-state secondary battery. The electrode composition contains a sulfide-based inorganic solid electrolyte, a polymer binder, an active material having a specific surface area of 10 m ² /g or more, and a dispersion medium, and the polymer forming the polymer binder has an SP value of 19.0 MPa ^{1 /2} or more components derived from (meth)acrylic monomers or vinyl monomers.

Description

Electrode composition, electrode sheet for all-solid-state secondary battery, all-solid-state secondary battery, and And electrode sheet for all-solid-state secondary battery and manufacturing method of all-solid-state secondary battery

technical field

The present invention relates to an electrode composition, an electrode sheet for an all-solid-state secondary battery, an all-solid-state secondary battery, an electrode sheet for an all-solid-state secondary battery, and a manufacturing method for the all-solid-state secondary battery.

Background technique

In an all-solid-state secondary battery, all the negative electrodes, electrolytes, and positive electrodes are made of solids, so that the safety and reliability of the batteries using the organic electrolyte solution can be greatly improved. And can also prolong life. In addition, the all-solid-state secondary battery can have a structure in which electrodes and electrolytes are directly arranged and arranged in series. Therefore, it is possible to achieve higher energy density than secondary batteries using an organic electrolyte solution, and application to electric vehicles, large storage batteries, and the like is expected.

The constituent layers (solid electrolyte layer, negative electrode active material layer, positive electrode active material layer, etc.) of such an all-solid-state secondary battery are formed of solid particles (inorganic solid electrolyte, active material, conductive aid, etc.). Therefore, the interfacial contact state of solid particles is limited, and the interface resistance is likely to increase (decrease in ionic conductivity). In addition, when charging and discharging are repeated, voids are formed between solid particles, resulting in an increase in interface resistance, resulting in a decrease in cycle characteristics of the all-solid-state secondary battery.

With regard to such an increase in interface resistance, the use of a sulfide-based inorganic solid electrolyte that exhibits high ionic conductivity adjacent to an organic electrolyte even in an inorganic solid electrolyte is expected. In addition, it has been reported that an active material having an increased specific surface area can suppress an increase in interface resistance, thereby improving the cycle characteristics of an all-solid-state secondary battery. As a material (active material layer forming material) forming a constituent layer of an all-solid-state secondary battery using such a sulfide-based inorganic solid electrolyte and an active material having a large specific surface area, for example, Patent Document 1 describes a mixed powder , which contains 45.7% by mass of Si spherical particle powder with a specific surface area of 20 m ² /g as a negative electrode active material, 45.7% by mass of a sulfide-based inorganic solid electrolyte, and 5% by mass of acetylene black as a conductive aid (Comparative Example 1).

Previous technical literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2019-186212

SUMMARY OF THE INVENTION

The technical problem to be solved by the invention

However, as a result of studies conducted by the present inventors, it has been found that a new problem arises in that the specific surface area of the active material is increased in the active material layer forming material containing the sulfide-based inorganic solid electrolyte and the active material.

That is, for an active material that is inherently difficult to disperse with respect to a dispersion medium, if the specific surface area is increased, the dispersibility of the active material immediately after preparation is further reduced, and in addition, the dispersibility immediately after preparation is stably maintained. The properties (dispersion stability) also deteriorated remarkably. In addition, as the surface area of the active material increases, the interface contact state not only with other solid particles but also with the current collector is significantly limited, and the adhesion force to them also decreases.

In this way, an active material with a large specific surface area itself is promising as a material capable of suppressing an increase in interface resistance, but Patent Document 1 has not studied from the above-mentioned viewpoint, and it is understood that in order to fully utilize the properties of an active material with a large specific surface area All-solid-state secondary batteries exhibiting excellent battery performance are important to solve the above-mentioned problems.

An object of the present invention is to provide an electrode composition that contains an active material having a large specific surface area, exhibits excellent dispersion stability, and can exhibit strong adhesion to a current collector while achieving An electrode layer (active material layer) with excellent cycle characteristics. Furthermore, an object of the present invention is to provide an electrode sheet for an all-solid-state secondary battery, an all-solid-state secondary battery, and an electrode sheet for an all-solid-state secondary battery, and a method for producing the all-solid-state secondary battery using the electrode composition.

Means for solving technical problems

As a result of continuing studies on electrode compositions, the present inventors have found that in the presence of a sulfide-based inorganic solid electrolyte, by using an active material having a specific surface area of 10 m ² /g or more in combination with an SP value of 19.0 MPa ¹ Binders composed of polymers derived from structural components such as (meth)acrylic monomers, etc. ^/2 or more, can suppress the passage of time over time even if it is an active material having a large specific surface area of 10 m ² /g or more. Re-agglomeration or precipitation is generated, and the excellent dispersibility immediately after preparation can be maintained. In addition, it was found that by using the electrode composition as a material for forming an active material layer, it is possible to exhibit strong adhesion to the current collector and to effectively suppress the decrease in discharge capacity due to charge and discharge (exhibits excellent cycle characteristics) all-solid-state secondary batteries. Based on these findings, the present invention has been further studied, and the present invention has been completed.

That is, the above-mentioned problem is solved by the following means.

<1> An electrode composition comprising a sulfide-based inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a polymer binder, an active material, and a dispersion medium An electrode composition for an all-solid-state secondary battery, wherein,

The above-mentioned active material has a specific surface area of 10 m ² /g or more,

The polymer forming the above-mentioned polymer binder has a constituent component derived from a (meth)acrylic monomer or a vinyl monomer with an SP value of 19.0 MPa ^1/2 or more.

<2> The electrode composition according to <1>, wherein

The polymeric binder dissolves in the dispersion medium.

<3> The electrode composition according to <1> or <2>, wherein

The active material has silicon element as a constituent element.

<4> The electrode composition according to any one of <1> to <3>, wherein

The said constituent has a polar group or a heterocyclic group containing active hydrogen.

<5> The electrode composition according to any one of <1> to <4>, wherein

The constituent component has a structure represented by the following formula (M1) or formula (M2).

[Chemical formula 1]

In formula (M1) and formula (M2), R, R ¹ , R ² and R ³ represent a hydrogen atom or a substituent.

L represents a linking group. L ¹ , L ² and L ³ represent a single bond or a linking group.

X represents -O-, -S- or -NR ^M -, and ^RM represents a hydrogen atom or a substituent.

Z represents -OH or -COOH.

<6> The electrode composition according to any one of <1> to <5>, wherein

The polymers forming the polymeric binder are (meth)acrylic polymers or vinyl polymers.

<7> The electrode composition according to any one of <1> to <6>, which contains a conductive aid.

<8> An electrode sheet for an all-solid-state secondary battery having a layer composed of the electrode composition according to any one of the above-mentioned <1> to <7> on the surface of the current collector.

<9> An all-solid-state secondary battery comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order, wherein,

At least one layer of the positive electrode active material layer and the negative electrode active material layer is composed of the electrode composition according to any one of <1> to <7>.

<10> A method for producing an electrode sheet for an all-solid-state secondary battery, comprising forming a film of the electrode composition according to any one of the above <1> to <7> on the surface of a current collector.

<11> A manufacturing method of an all-solid-state secondary battery, which manufactures an all-solid-state secondary battery through the manufacturing method described in the above-mentioned <10>.

Invention effect

The present invention can provide an electrode composition that can form an electrode layer that contains an active material with a large specific surface area, has excellent dispersion stability, exhibits strong adhesion to a current collector, and can also achieve excellent cycle characteristics. Furthermore, the present invention can provide an electrode sheet for an all-solid-state secondary battery and an all-solid-state secondary battery having an electrode layer composed of the electrode composition. Furthermore, the present invention can provide an electrode sheet for an all-solid-state secondary battery and a method for producing an all-solid-state secondary battery using the electrode composition.

The above-described features and other features and advantages of the present invention will become more apparent from the following description with appropriate reference to the accompanying drawings.

Description of drawings

FIG. 1 is a vertical cross-sectional view schematically showing an all-solid-state secondary battery according to a preferred embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view schematically showing a coin-type all-solid-state secondary battery produced in an example.

Detailed ways

In this invention, the numerical range represented by "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

In the present invention, the expression about a compound (for example, when the compound is referred to at the end) means that the compound itself includes its salt and its ion in addition to the compound itself. In addition, the term includes derivatives in which some of the introduced substituents and the like are changed within a range that does not impair the effects of the present invention.

In the present invention, (meth)acrylic acid refers to one or both of acrylic acid and methacrylic acid. The same is true for (meth)acrylates.

In the present invention, a substituent, a linking group, etc. (hereinafter referred to as a substituent etc.) which are not clearly described as substituted or unsubstituted means that the group may have an appropriate substituent. Therefore, in the present invention, even if it is simply described as a YYY group, the YYY group includes a form having a substituent in addition to a form having no substituent. This also has the same meaning for compounds in which substitution or unsubstitution is not explicitly described. As a preferable substituent, the substituent T mentioned later is mentioned, for example.

In the present invention, when there are a plurality of substituents etc. represented by a specific symbol or when a plurality of substituents etc. are specified simultaneously or selectively, it means that the respective substituents etc. may be the same or different from each other. In addition, even if there is no particular description, when a plurality of substituents and the like are adjacent, it means that these may be linked or condensed to each other to form a ring.

In the present invention, the polymer refers to a polymer, but has the same meaning as the so-called high molecular compound. In addition, the polymer binder refers to a binder composed of a polymer, and includes the polymer itself and the binder formed by containing the polymer.

In the present invention, a composition containing an active material and used as a material for forming an active material layer of an all-solid-state secondary battery (active material layer forming material) is referred to as an electrode composition. On the other hand, a composition containing a sulfide-based inorganic solid electrolyte and used as a material for forming a solid electrolyte layer of an all-solid-state secondary battery is referred to as a (sulfide-based) inorganic solid electrolyte-containing composition, which generally does not contain active substance.

In the present invention, the electrode composition includes a positive electrode composition containing a positive electrode active material and a negative electrode composition containing a negative electrode active material. Therefore, either or both of the positive electrode composition and the negative electrode composition are simply collectively referred to as an electrode composition. Furthermore, in the present invention, either or both of the positive electrode active material layer and the negative electrode active material layer may be simply collectively referred to as an active material layer or an electrode active material layer, and the positive electrode active material and the negative electrode active material may be collectively referred to as an active material layer or an electrode active material layer. Either or both are simply collectively referred to as active material or electrode active material.

[Electrode composition]

The electrode composition of the present invention contains a sulfide-based inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a polymer binder, an active material, and a dispersion medium.

In this electrode composition, from the viewpoints of initial dispersibility and dispersion stability (these are collectively referred to as dispersion characteristics) immediately after the electrode composition (especially active material) is prepared, the polymer binder is preferably adsorbed on Active material, but may or may not be adsorbed to the sulfide-based inorganic solid electrolyte. The electrode composition of the present invention is preferably a slurry in which an active material and a sulfide-based inorganic solid electrolyte are dispersed in a dispersion medium. In this case, the polymer binder preferably has a function of dispersing the solid particles in the dispersion medium.

In the active material layer, the polymer binder functions as a binder that binds the active material, the sulfide-based inorganic solid electrolyte, and even solid particles such as a conductive assistant that can coexist with each other. In addition, it also functions as a binder for binding the current collector and the solid particles. In the electrode composition, the polymer binder may or may not have the function of binding the solid particles to each other.

The electrode composition of the present invention contains an active material having a large specific surface area and is also excellent in dispersion stability. By using this electrode composition as an active material layer-forming material, it is possible to realize an active material that exhibits strong binding force (adhesion force) to the current collector on the surface of the current collector and can realize excellent cycle characteristics A layered all-solid-state secondary battery electrode sheet, and an all-solid-state secondary battery excellent in cycle characteristics.

The detailed reason for this is not clear, but is considered as follows. That is, the active material layer containing the active material having a large specific surface area of 10 m ² /g or more constitutes many conduction paths of lithium ions based on the active material. Therefore, even if part of the conduction paths are blocked (collapsed) by repeated charging and discharging, most of the remaining conduction paths are still connected. Furthermore, in order to satisfy the high demand for all-solid-state secondary batteries in recent years, it is considered that the breakdown of the conduction path can be suppressed even if high-speed charge and discharge at a large current are repeated.

On the other hand, in the electrode composition, it is considered that the constituent component of the polymer binder derived from a specific monomer having an SP value of 19.0 MPa ^1/2 or more and the surface of the active material (usually, it has an oxidized polarity The interaction of the higher part) is strengthened. Therefore, the polymer binder promotes the adsorption of the active material in the electrode composition, and even the active material having a large specific surface area of 10 m ² /g or more can be highly dispersed (excellent in initial dispersibility), and can Re-agglomeration or precipitation over time is suppressed (exhibits excellent dispersion stability).

In addition, it is considered that the above-mentioned adsorption state is maintained in the active material layer, and each component is unlikely to be unevenly distributed in the active material layer, and sufficient contact (adhesion) between the polymer binder and the current collector can be ensured. Thereby, not only the adhesive force between the active materials but also the adhesive force with the current collector can be strengthened. Therefore, generation of voids due to expansion and contraction of the active material can be effectively suppressed in high-speed charge and discharge under large currents in addition to charge and discharge under normal conditions, and excellent cycle characteristics can be realized.

In the present invention, as long as the polymer binder and the active material are adsorbed, the above-mentioned interaction is not particularly limited, and may be chemical interaction or physical interaction.

The details of the above reasons have been described focusing on the active material with a large specific surface area and the polymer binder. It is considered that dispersion caused by solid particles (sulfide-based inorganic solid electrolytes, conductive additives, etc.) coexisting with the active material Influences such as a decrease in stability and adhesion are small, and the polymer binder also acts on these solid particles in the same manner as the active material, thereby exhibiting the above-mentioned effects.

Since the electrode composition of the present invention exhibits the above-mentioned excellent properties, it can be preferably used as an electrode sheet for an all-solid-state secondary battery or an active material layer-forming material for an all-solid-state secondary battery. In particular, it can be preferably used as a material for forming a negative electrode sheet for an all-solid-state secondary battery or a negative electrode active material layer containing a negative electrode active material that expands and shrinks greatly due to charge and discharge, and excellent cycle characteristics can also be achieved in this form.

The electrode composition of the present invention is preferably a non-aqueous composition. In the present invention, the non-aqueous composition includes an aspect in which the moisture content (also referred to as a moisture content) is preferably 500 ppm or less, in addition to the aspect that does not contain moisture. In the non-aqueous composition, the water content is more preferably 200 ppm or less, still more preferably 100 ppm or less, and particularly preferably 50 ppm or less. When the electrode composition is a non-aqueous composition, the deterioration of the sulfide-based inorganic solid electrolyte can be suppressed. The water content represents the amount of water contained in the electrode composition (mass ratio to the electrode composition), and specifically, it is determined by filtration with a 0.02 μm membrane filter and measured by Karl Fischer titration. value.

Hereinafter, components contained in the electrode composition of the present invention and components that may be contained will be described.

<Sulfide-based inorganic solid electrolyte>

The electrode composition of the present invention contains a sulfide-based inorganic solid electrolyte. When the electrode composition contains the sulfide-based inorganic solid electrolyte, the formed electrode active material layer has excellent deformability, and the contact area between solid particles such as the sulfide-based inorganic solid electrolyte and the active material in the layer can be increased, and furthermore, it is possible to increase the The contact area between the current collector and the electrode active material layer is increased. Therefore, when a sulfide-based inorganic solid electrolyte is used, the ion conduction path formed in the electrode active material layer and between the current collectors can be increased, and the construction of the ion conduction path when an active material with a low specific surface area is used can be promoted. Effect.

In the present invention, the inorganic solid electrolyte refers to an inorganic solid electrolyte, and the solid electrolyte refers to a solid electrolyte capable of moving ions in the interior. Considering that no organic matter is contained as the main ion conductive material, it is compatible with organic solid electrolytes (polymer electrolytes represented by polyethylene oxide (PEO), etc., lithium bis(trifluoromethanesulfonyl)imide) ( Organic electrolyte salts represented by LiTFSI) and the like) are clearly distinguished. In addition, since the inorganic solid electrolyte is solid in a stable state, it is generally not dissociated or dissociated into cations and anions. In this regard, it is clearly related to inorganic electrolyte salts (LiPF ₆ , LiBF ₄ , lithium bis(fluorosulfonyl)imide (LiFSI), LiCl, etc.) that dissociate or dissociate into cations and anions in electrolytes or polymers. be differentiated. The sulfide-based inorganic solid electrolyte is not particularly limited as long as it has conductivity of ions of metals belonging to Group 1 or Group 2 of the periodic table, and generally does not have electron conductivity. When the all-solid-state secondary battery of the present invention is a lithium ion battery, the sulfide-based inorganic solid electrolyte preferably has ion conductivity of lithium ions.

As the sulfide-based inorganic solid electrolyte, a sulfide-based inorganic solid electrolyte material generally used for all-solid-state secondary batteries can be appropriately selected and used.

Preferably, the sulfide-based inorganic solid electrolyte contains a sulfur atom, has ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and has electronic insulating properties. The sulfide-based inorganic solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may contain other elements other than Li, S, and P depending on the purpose and circumstances.

As the sulfide-based inorganic solid electrolyte, for example, a lithium ion-conductive sulfide-based inorganic solid electrolyte that satisfies the composition represented by the following formula (S1) can be mentioned.

L _a1 M _b1 P _c1 S _d1 A _e1 (S1)

In formula (S1), L represents an element selected from the group consisting of Li, Na and K, preferably Li. M represents an element selected from the group consisting of B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. A represents an element selected from the group consisting of I, Br, Cl and F. a1 to e1 represent the composition ratio of each element, and a1:b1:c1:d1:e1 satisfies 1 to 12:0 to 5:1:2 to 12:0 to 10. a1 is preferably 1 to 9, more preferably 1.5 to 7.5. b1 is preferably 0-3, more preferably 0-1. d1 is preferably 2.5 to 10, and more preferably 3.0 to 8.5. e1 is preferably 0-5, more preferably 0-3.

As described below, the composition ratio of each element can be controlled by adjusting the compounding amount of the raw material compound in the production of the sulfide-based inorganic solid electrolyte.

The sulfide-based inorganic solid electrolyte may be amorphous (glass), may be crystallized (glass-ceramic), or only a part of it may be crystallized. For example, Li-P-S-based glass containing Li, P, and S, or Li-P-S-based glass ceramics containing Li, P, and S can be used.

The sulfide-based inorganic solid electrolyte can be prepared by, for example, lithium sulfide (Li ₂ S), phosphorus sulfide (eg, phosphorus pentasulfide (P ₂ S ₅ )), monomeric phosphorus, monomeric sulfur, sodium sulfide, hydrogen sulfide, lithium halide ( For example, LiI, LiBr, LiCl) and the sulfide of the element represented by M (for example, SiS ₂ , SnS, GeS ₂ ) are reacted to produce at least two or more kinds of raw materials.

In the Li-PS-based glass and the Li-PS-based glass ceramics, the ratio of Li ₂ S to P ₂ S ₅ is preferably 60:40 to 90:10 in terms of the molar ratio of Li ₂ S:P ₂ S ₅ , and more preferably From 68:32 to 78:22. By setting the ratio of Li ₂ S and P ₂ S ₅ to this range, the lithium ion conductivity can be improved. Specifically, the lithium ion conductivity can be preferably set to 1×10 ^-4 S/cm or more, and more preferably 1×10 ^-3 S/cm or more. Although the upper limit is not particularly set, it is actually 1×10 ^-1 S/cm or less.

As a specific example of the sulfide-based inorganic solid electrolyte, the combination of raw materials is shown below. For example, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiCl, Li ₂ SP ₂ S ₅ -H ₂ S, Li ₂ SP ₂ S ₅ -H ₂ S-LiCl, Li ₂ S-LiI -P ₂ S ₅ , Li ₂ S-LiI-Li ₂ OP ₂ S ₅ , Li ₂ S-LiBr-P ₂ S ₅ , Li ₂ S-Li ₂ OP ₂ S ₅ , Li ₂ S-Li ₃ PO ₄ - P ₂ S ₅ , Li ₂ SP ₂ S ₅ -P ₂ O ₅ , Li ₂ SP ₂ S ₅ -SiS ₂ , Li ₂ SP ₂ S ₅ -SiS ₂ -LiCl, Li ₂ SP ₂ S ₅ -SnS, Li ₂ SP ₂ S ₅ -Al ₂ S ₃ , Li ₂ S-GeS ₂ , Li ₂ S-GeS ₂ -ZnS, Li ₂ S-Ga ₂ S ₃ , Li ₂ S-GeS ₂ -Ga ₂ S ₃ , Li ₂ S -GeS ₂ -P ₂ S ₅ , Li ₂ S-GeS ₂ -Sb ₂ S ₅ , Li ₂ S-GeS ₂ -Al ₂ S ₃ , Li ₂ S-SiS ₂ , Li ₂ S-Al ₂ S ₃ , Li ₂ S-SiS ₂ -Al ₂ S ₃ , Li ₂ S-SiS ₂ -P ₂ S ₅ , Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ S-SiS ₂ -LiI, Li ₂ S- SiS ₂ -Li ₄ SiO ₄ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₁₀ GeP ₂ S ₁₂ and the like. However, the mixing ratio of each raw material is not limited. As a method of synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition, for example, an amorphization method can be mentioned. As an amorphization method, a mechanical polishing method, a solution method, and a melt quenching method are mentioned, for example. The processing at normal temperature can be performed, and the simplification of the manufacturing process can be achieved.

The sulfide-based inorganic solid electrolyte is preferably particles. The shape of the particles is not particularly limited, and may be flat, amorphous, or the like, but preferably spherical or granular.

The average particle diameter (volume average particle diameter) of the sulfide-based inorganic solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.1 μm or more. The upper limit is preferably 100 μm or less, and more preferably 50 μm or less.

The measurement of the average particle diameter of the sulfide-based inorganic solid electrolyte is performed by the following procedure. In a 20 mL sample bottle, the sulfide-based inorganic solid electrolyte particles were diluted with water (heptane in the case of a substance unstable to water) to prepare a 1 mass % dispersion liquid sample. The diluted dispersion liquid sample was irradiated with ultrasonic waves at 1 kHz for 10 minutes, and then immediately used in the test. Using this dispersion liquid sample, data collection was performed 50 times using a laser diffraction/scattering particle size distribution analyzer LA-920 (trade name, manufactured by HORIBA, Ltd.) at a temperature of 25° C. using a quartz cell for measurement, thereby The volume average particle diameter is obtained. For other detailed conditions and the like, as necessary, refer to the description in Japanese Industrial Standard (JIS) Z8828:2013 "Particle Size Analysis-Dynamic Light Scattering Method". Five samples were made for each grade and the average value was used.

The specific surface area of the sulfide-based inorganic solid electrolyte generally has a value smaller than the specific surface area of the active material described later, but is not limited to this, and can be appropriately set.

The sulfide-based inorganic solid electrolyte may contain one type or two or more types.

The content of the sulfide-based inorganic solid electrolyte in the electrode composition is not particularly limited, but from the viewpoint of adhesion and dispersibility, it is preferably 50% by mass or more in total with the active material in 100% by mass of the solid content , more preferably 70% by mass or more, particularly preferably 90% by mass or more. From the same viewpoint, the upper limit is preferably 99.9 mass % or less, more preferably 99.5 mass % or less, and particularly preferably 99 mass % or less. Only the content of the sulfide-based inorganic solid electrolyte in the electrode composition is appropriately set so that the total content of the active materials falls within the above-mentioned range.

In the present invention, the solid content refers to a component that volatilizes or evaporates without disappearing when the electrode composition is dried at 150° C. for 6 hours under a nitrogen atmosphere under a pressure of 1 mmHg. Typically, it refers to components other than the dispersion medium described later.

＜Active Substance＞

The electrode composition of the present invention contains an active material capable of intercalating and deintercalating an ion of a metal belonging to Group 1 or Group 2 of the periodic table.

The active material contained in the electrode composition of the present invention is in the form of particles at least in the electrode composition. The shape of the particles is not particularly limited, and may be flat, amorphous, or the like, but preferably spherical or granular.

The active material (particle) has a specific surface area of 10 m ² /g or more. In the present invention, by using together with a polymer binder described later, the significantly low dispersion properties of the active material having a large specific surface area can be improved, and the active material having such a large specific surface area can be used. Therefore, an active material layer containing an active material having a specific surface area of 10 m ² /g or more is constructed with a plurality of conduction paths for lithium ions, and an all-solid-state secondary battery that exhibits excellent cycle characteristics can be realized.

The specific surface area of the active material is preferably set within a range in which an improvement in dispersion characteristics and an improvement in cycle characteristics can be achieved in a balanced manner. The lower limit value thereof is preferably 12 m ² /g or more, more preferably 15 m ² /g or more, and further preferably 20 m ² /g or more. On the other hand, the upper limit is preferably 50 m ² /g or less, more preferably 45 m ² /g or less, and further preferably 40 m ² /g or less.

In the present invention, the specific surface area refers to the BET specific surface area, and is a value calculated by the BET (one point) method based on the nitrogen adsorption method. Specifically, it is assumed that the active material extracted from the active material used in the electrode composition, the electrode sheet for all-solid-state secondary batteries, or the active material layer of the all-solid-state secondary battery is as follows, using the following measuring apparatus according to the following value measured under the above conditions.

-Measurement method of BET specific surface area-

Specific surface area/pore distribution measuring apparatus: Measured by a gas adsorption method (nitrogen gas) using BELSORP MINI (trade name, manufactured by MicrotracBEL). 0.3 g of the active material was put into a sample tube with an inner diameter of 3.6 mm, and what was dried by blowing nitrogen gas at 80° C. for 6 hours was used for the measurement.

-Method for extracting active substance from active substance layer-

0.5 g of the active material layer was added to 50 g of butyl butyrate, followed by centrifugation at 3000 rpm for 1 hour. 50 g of N-methylformamide was added to the precipitate obtained by separating the supernatant, and the mixture was stirred at room temperature for 1 hour. After centrifuging the thus obtained dispersion liquid at 5000 rpm for 1 hour, the supernatant liquid was separated to obtain a precipitate. This precipitate was washed twice with 25 g of N-methylformamide, and then vacuum-dried at 100° C. for 2 hours to obtain an active material extracted from the active material layer.

As the active material having the specific surface area in the above-mentioned range, a commercially available product may be used, or an appropriately prepared product may be used. The method for adjusting the specific surface area is not particularly limited, and a well-known method can be applied, for example, the method for adjusting the average particle diameter, the modification conditions, and the like, which will be described later.

The average particle diameter of the active material used in the present invention is not particularly limited, and can be appropriately set in consideration of specific surface area and the like. For example, from the viewpoint of both dispersion characteristics and cycle characteristics, the thickness is preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.6 μm or less. The lower limit of the average particle diameter is actually 0.01 μm or more, for example, preferably 0.03 μm or more, and more preferably 0.05 μm or more.

The average particle diameter of the active material can be measured in the same manner as the average particle diameter of the sulfide-based inorganic solid electrolyte.

There is no restriction|limiting in particular in the adjustment method of an average particle diameter, A well-known method can be applied, For example, the method using a normal pulverizer or a classifier is mentioned. As a pulverizer or a classifier, for example, a mortar, a ball mill, a sand mill, a vibration ball mill, a satellite ball mill, a planetary ball mill, a rotary air jet mill, a sieve, etc. can be appropriately used. At the time of pulverization, wet pulverization in which a dispersion medium such as water or methanol is coexisted can be appropriately performed. In order to obtain a desired average particle diameter, classification is preferably performed. The classification is not particularly limited, and can be performed using a sieve, an air classifier, or the like. Both dry and wet classifications can be used.

As an active material, a negative electrode active material and a positive electrode active material are mentioned.

(negative electrode active material)

The negative electrode active material is an active material that can intercalate and deintercalate an ion of a metal belonging to Group 1 or Group 2 of the periodic table, and is preferably an active material that can reversibly intercalate and deintercalate lithium ions. The material is not particularly limited as long as it has the above-mentioned properties, and examples thereof include carbonaceous materials, metal oxides, metal composite oxides, lithium alone, lithium alloys, and negative electrodes capable of forming an alloy with lithium (alloying). active substances, etc. Among them, from the viewpoint of reliability, it is preferable to use a carbonaceous material, a metal composite oxide, or a single lithium. From the viewpoint that the capacity of the all-solid-state secondary battery can be increased, an active material that can be alloyed with lithium is preferable. Since the active material layer formed of the electrode composition of the present invention can maintain a strong binding state between solid particles, a negative electrode active material capable of forming an alloy with lithium can be used as the negative electrode active material. Thereby, the capacity of the all-solid-state secondary battery can be increased and the life of the battery can be prolonged.

The carbonaceous material used as the negative electrode active material refers to a material substantially composed of carbon. For example, various synthetic resins such as petroleum pitch, carbon black such as acetylene black (AB), graphite (natural graphite, artificial graphite such as vapor-grown graphite, etc.), and PAN (polyacrylonitrile)-based resin or furfuryl alcohol resin can be calcined. made of carbonaceous materials. In addition, various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and activated carbon fibers, and mesophases can also be used. Tiny spheres, graphite whiskers, and flat graphite, etc.

These carbonaceous materials are classified into hardly graphitizable carbonaceous materials (also referred to as hard carbon.) and graphite-based carbonaceous materials by the degree of graphitization. In addition, the carbonaceous material preferably has the interplanar spacing, density, and crystallite size described in JP 62-22066 A, JP 2-6856 A, and JP 3-45473 A. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP 5-90844 A, graphite having a coating layer described in JP 6-4516 A, or the like can be used.

As the carbonaceous material, hard carbon or graphite is preferably used, and graphite is more preferably used.

The oxide of metal or semi-metal element suitable for the negative electrode active material is not particularly limited as long as it can absorb and release lithium, and oxides of metal elements (metal oxides), metal Complex oxides or complex oxides of metal elements and semi-metal elements (collectively referred to as metal complex oxides.), oxides of semi-metal elements (semi-metal oxides). As these oxides, amorphous oxides are preferred, and chalcogenides, which are reaction products of metal elements and elements of Group 16 of the periodic table, are also preferred. In the present invention, a semi-metal element refers to an element that exhibits an intermediate property between a metal element and a non-semi-metal element, and usually includes six elements of boron, silicon, germanium, arsenic, antimony, and tellurium, and further includes selenium, polonium, and astatine 3 elements. In addition, amorphous refers to a material having a broad scattering band having an apex in a region of 20° to 40° in 2θ value by X-ray diffractometry using CuKα rays, and may have crystalline diffraction lines. The strongest intensity among the crystalline diffraction lines appearing in the region with the 2θ value of 40° to 70° is preferably equal to the intensity of the diffraction line at the apex of the broad scattering band appearing in the region with the 2θ value of 20° to 40°. 100 times or less, more preferably 5 times or less, and particularly preferably a diffraction line without crystallinity.

In the compound group containing the above-mentioned amorphous oxide and chalcogenide, an amorphous oxide of a semi-metal element or the above-mentioned chalcogenide is still more preferable, and a compound selected from Groups 13(IIIB) to 15 of the periodic table is particularly preferable. A (complex) oxide or chalcogenide of an element of group (VB) (eg, Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi) alone or in combination of two or more thereof. Specific examples of preferable amorphous oxides and chalcogenides include Ga ₂ O ₃ , GeO, PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , and Sb ₂ O, for example. ₃ , Sb ₂ O ₄ , Sb ₂ O ₈ Bi ₂ O ₃ , Sb ₂ O ₈ Si ₂ O ₃ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , GeS, PbS, PbS ₂ , Sb ₂ S ₃ or Sb ₂ S ₅ .

As the negative electrode active material that can be used together with an amorphous oxide centered on Sn, Si, and Ge, carbonaceous materials, lithium monomers, and lithium alloys that can absorb and/or release lithium ions or lithium metals are preferably used. , A negative electrode active material capable of alloying with lithium.

From the viewpoint of high current density charge-discharge characteristics, oxides of metal or semimetal elements, especially metal (complex) oxides and the aforementioned chalcogenides preferably contain at least one of titanium and lithium as constituent components. The lithium-containing metal composite oxide (lithium composite metal oxide) includes, for example, a composite oxide of lithium oxide and the above-mentioned metal (composite) oxide or the above-mentioned chalcogenide, and more specifically, Li ₂ SnO ₂ .

The negative electrode active material such as metal oxide preferably contains titanium element (titanium oxide). Specifically, since Li ₄ Ti ₅ O ₁₂ (lithium titanate [LTO]) has a small volume change when adsorbing and deintercalating lithium ions, it is excellent in high-speed charge-discharge characteristics, suppresses deterioration of electrodes, and increases lithium ion ions The life of the secondary battery is preferable in terms of these two points.

The lithium alloy used as the negative electrode active material is not particularly limited as long as it is an alloy generally used as a negative electrode active material of a secondary battery.

The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is a negative electrode active material generally used as a secondary battery. Such an active material expands and shrinks greatly due to charging and discharging of an all-solid-state secondary battery, and accelerates the degradation of cycle characteristics. However, the electrode composition of the present invention contains a polymer binder described later for the active material combination, so it can effectively Degradation of cycle characteristics due to charge and discharge is effectively suppressed. Examples of such active materials include (negative electrode) active materials (alloys, etc.) containing silicon element or tin element, and various metals such as Al and In, and preferably a negative electrode active material containing silicon element that can realize higher battery capacity (Silicon element-containing active material) More preferably, it is a silicon element-containing active material whose content of silicon element is 50 mol % or more of all constituent elements.

In general, negative electrodes containing these negative electrode active materials (for example, Si negative electrodes containing an active material containing silicon element, Sn negative electrodes containing an active material containing tin element, etc.) can absorb carbon negative electrodes (graphite, acetylene black, etc.) more Li ions. That is, the storage amount of Li ions per unit mass increases. Therefore, the battery capacity (energy density) can be increased. As a result, there is an advantage that the battery driving time can be extended.

Examples of the silicon-containing active material include silicon materials such as Si and SiOx (0<x≤1), and silicon-containing alloys (for example, titanium, vanadium, chromium, manganese, nickel, copper, lanthanum, etc.) LaSi ₂ , VSi ₂ , La-Si, Gd-Si, Ni-Si) or textured active materials (eg, LaSi ₂ /Si), and active materials containing elements of silicon and tin such as SnSiO ₃ and SnSiS ₃ Wait. In addition, SiOx itself can be used as a negative electrode active material (semi-metal oxide), and since Si is generated by the operation of an all-solid-state secondary battery, it can be used as a negative electrode active material (a precursor thereof) that can be alloyed with lithium. substance).

Examples of the negative electrode active material having a tin element include Sn, SnO, SnO ₂ , SnS, SnS ₂ , and active materials containing the above-mentioned silicon element and tin element. In addition, a composite oxide with lithium oxide, for example, Li ₂ SnO ₂ can also be used.

In the present invention, the above-mentioned negative electrode active material can be used without particular limitation, but from the viewpoint of battery capacity, as the negative electrode active material, a negative electrode active material that can be alloyed with lithium is preferable, and among them, the above-mentioned negative electrode active material is more preferable. More preferably, the silicon material or the silicon-containing alloy (alloy containing silicon element) contains silicon (Si) or the silicon-containing alloy.

The negative electrode active material contained in the electrode composition may be one type or two or more types.

When forming the negative electrode active material layer, the mass (mg) (weight per unit area) of the negative electrode active material per unit area (cm ² ) of the negative electrode active material layer is not particularly limited. It can be appropriately determined according to the designed battery capacity, and can be set to, for example, 1 to 100 mg/cm ² .

The content of the negative electrode active material in the electrode composition is not particularly limited, but is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, more preferably 30 to 80% by mass, and more preferably 100% by mass of the solid content. Preferably it is 40-75 mass %.

(positive electrode active material)

The positive electrode active material is an active material that can intercalate and deintercalate an ion of a metal belonging to Group 1 or Group 2 of the periodic table, and is preferably an active material that can reversibly intercalate and deintercalate lithium ions. The material is not particularly limited as long as it has the above-mentioned properties, and may be a transition metal oxide or an organic substance that decomposes the battery, an element capable of complexing with Li, such as sulfur.

Among them, as the positive electrode active material, transition metal oxides are preferably used, and transition metal oxides having transition metal elements ^Ma (one or more elements selected from Co, Ni, Fe, Mn, Cu, and V) are more preferred. In addition, the transition metal oxide may be mixed with elements M ^b (elements of Group 1(Ia) of the periodic table of metals, elements of Group 2(IIa), Al, Ga, In, Ge, elements such as Sn, Pb, Sb, Bi, Si, P and B). The mixing amount is preferably 0 to 30 mol % with respect to the amount (100 mol %) of the transition metal element ^Ma . It is more preferable to mix and synthesize so that the molar ratio of Li/M ^a may be 0.3 to 2.2.

Specific examples of transition metal oxides include (MA) transition metal oxides having a layered rock salt structure, (MB) transition metal oxides having a spinel structure, (MC) transition metal phosphate compounds containing lithium , (MD) lithium-containing transition metal halogenated phosphoric acid compounds and (ME) lithium-containing transition metal silicic acid compounds, etc.

Specific examples of (MA) transition metal oxides having a layered rock-salt structure include LiCoO ₂ (lithium cobaltate [LCO]), LiNi ₂ O ₂ (lithium nickelate), LiNi _0.85 Co _0.10 Al _0.05 O ₂ (lithium nickel cobalt aluminate [NCA]), LiNi _1/3 Co _1/3 Mn _{1/ 3} O ₂ (lithium nickel manganese cobalt oxide [NMC]), and LiNi _0.5 Mn _0.5 O ₂ (lithium manganese nickelate).

Specific examples of the transition metal oxide (MB) having a spinel structure include LiMn ₂ O ₄ (LMO), LiCoMnO ₄ , Li ₂ FeMn ₃ O ₈ , Li ₂ CuMn ₃ O ₈ , and Li ₂ CrMn ₃ O ₈ and Li ₂ NiMn ₃ O ₈ .

Examples of (MC) lithium-containing transition metal phosphate compounds include olivine-type iron phosphates such as LiFePO ₄ and Li ₃ Fe ₂ (PO ₄ ) ₃ , iron pyrophosphates such as LiFeP ₂ O ₇ , and phosphoric acids such as LiCoPO ₄ . Monoclinic NASICON type vanadium phosphate salts such as cobalt and Li ₃ V ₂ (PO ₄ ) ₃ (lithium vanadium phosphate).

Examples of (MD) lithium-containing transition metal halogenated phosphoric acid compounds include iron fluorophosphates such as Li ₂ FePO ₄ F, manganese fluorophosphates such as Li ₂ MnPO ₄ F, and cobalt fluorophosphates such as Li ₂ CoPO ₄ F. kind.

As (ME) lithium-containing transition metal silicate compounds, for example, Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO ₄ and the like can be mentioned.

In the present invention, (MA) is preferably a transition metal oxide having a layered rock-salt structure, more preferably LCO or NMC.

The positive electrode active material obtained by the calcination method can also be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, and an organic solvent.

The positive electrode active material contained in the electrode composition may be one type or two or more types.

When forming the positive electrode active material layer, the mass (mg) (weight per unit area) of the positive electrode active material per unit area (cm ² ) of the positive electrode active material layer is not particularly limited. It can be appropriately determined according to the designed battery capacity, and can be set to, for example, 1 to 100 mg/cm ² .

The content of the positive electrode active material in the electrode composition is not particularly limited, but is preferably 10 to 97% by mass, more preferably 30 to 95% by mass, still more preferably 40 to 93% by mass, and particularly preferably 100% by mass of solid content. Preferably it is 50-90 mass %.

As a measuring method, inductively coupled plasma (ICP) emission spectrometry can be used, and as a convenient method, the chemical formula of the compound obtained by the above-mentioned firing method can be calculated from the mass difference of the powder before and after firing.

(coating of active substance)

The surfaces of the positive electrode active material and the negative electrode active material may also be surface-coated with different metal oxides. As a surface coating agent, the metal oxide containing Ti, Nb, Ta, W, Zr, Al, Si, or Li, etc. are mentioned. Specifically, titanate spinel, tantalum-based oxide, niobium-based oxide, lithium niobate-based compound, etc. can be mentioned, and specifically, Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₂ O ₅ , LiTaO ₃ , LiNbO ₃ , LiAlO ₂ , Li ₂ ZrO ₃ , Li ₂ WO ₄ , Li ₂ TiO ₃ , Li ₂ B ₄ O ₇ , Li ₃ PO ₄ , Li ₂ MoO ₄ , Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , Li ₂ SiO ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , B ₂ O ₃ and the like.

Also, the surface of the electrode containing the positive electrode active material or the negative electrode active material may be surface-treated with sulfur or phosphorus.

Also, the surface of the particles of the positive electrode active material or the negative electrode active material may be subjected to surface treatment by actinic rays or active gas (plasma or the like) before and after the above-mentioned surface coating.

<Polymer binder>

The polymer binder (also referred to as a binder) contained in the electrode composition of the present invention is a binder used in combination with the above-mentioned active material having a specific surface area of 10 m ² /g or more, and interacts with the active material to improve dispersion stability in electrode compositions. In addition, the dispersion stability can be improved for solid particles other than the active material. In addition, by using a sulfide-based inorganic solid electrolyte and an active material together, high adhesion to the current collector, and even high adhesion of solid particles to each other, is exhibited.

The binder exhibits solubility in the dispersion medium contained in the electrode composition, and preferably dissolves. Thereby, the dispersion characteristics of the electrode composition can be further improved. In addition, the adhesion between the solid particles or the current collector can be further strengthened, and the effect of improving the cycle characteristics of the all-solid-state secondary battery can also be enhanced.

In the present invention, the fact that the binder dissolves in the dispersion medium is not limited to the form in which all the binders are dissolved in the dispersion medium, but for example, the solubility in the dispersion medium is 80% or more. The measurement method of solubility is as follows.

That is, a predetermined amount of the binder to be measured is weighed into a glass bottle, 100 g of a dispersion medium of the same type as the dispersion medium contained in the electrode composition is added thereto, and the mixture is placed on a mixing rotor at a temperature of 25°C. Stir at 80 rpm for 24 hours. The transmittance of the thus obtained mixed solution after stirring for 24 hours was measured under the following conditions. This test (transmittance measurement) was performed by changing the dissolved amount of the binder (predetermined amount), and the upper limit concentration X (mass %) at which the transmittance was 99.8% was defined as the solubility of the binder in the dispersion medium.

-Transmittance measurement conditions-

Dynamic Light Scattering (DLS) Measurement

Apparatus: DLS measuring apparatus DLS-8000 manufactured by Otsuka Electronics Co., Ltd.

Laser wavelength, output: 488nm/100mW

Sample cell: NMR tube

In the present invention, when the binder does not exhibit the aforementioned solubility to the dispersion medium contained in the electrode composition, the binder is preferably present in the form of particles in the electrode composition (dispersion medium). The shape is not particularly limited, and may be flat, amorphous, or the like, but preferably spherical or granular. In this case, in the electrode composition, the average particle diameter of the particulate binder is not particularly limited, but is preferably 10 nm or more, more preferably 50 nm or more, and further preferably 200 nm or more. The upper limit is preferably 5 μm or less, more preferably 1 μm or less, and further preferably 500 nm or less. The average particle diameter of the binder can be measured in the same manner as the average particle diameter of the above-mentioned inorganic solid electrolyte. The average particle diameter of the binder can be adjusted, for example, by the type of dispersion medium, the composition of the binder-forming polymer, and the like.

(polymers that form polymer binders)

The polymer that forms a polymer binder (also referred to as a binder-forming polymer.) may have a structure derived from a (meth)acrylic monomer or vinyl monomer with an SP value of 19.0 MPa ^1/2 or more The components are not particularly limited, and as will be described later, a (meth)acrylic polymer or a vinyl polymer is preferably used.

The polymer which forms a polymer binder may be 1 type, and may be 2 or more types.

The constituent component which the binder-forming polymer has at least is a component derived from a monomer having an SP value of 19.0 MPa ^1/2 or more. The constituent derived from a monomer having such an SP value is not particularly limited, and may not have a polar group (eg, an alkyl group having 1 to 6 carbon atoms), but preferably has a polar group. As described above, the alkyl group or the polar group interacts with the surface of the above-mentioned active material having a specific surface area of 10 m ² /g or more, thereby adsorbing the binder to the active material.

When the SP value of the monomer derived from the above-mentioned constituents (including constituents without polar groups, but sometimes referred to as constituents containing polar groups for convenience) is 19.0 MPa ^1/2 or more, then It is possible to improve the dispersion properties of the solid particles, especially the active material, and to strengthen the adhesive force. From the viewpoint of further improving the dispersion properties and adhesion of solid particles, especially active materials, it is preferably 19.5 MPa ^1/2 or more, more preferably 20.0 MPa ^1/2 or more, and even more preferably 20.5 MPa ^1/2 or more. The upper limit of the SP value can be appropriately set according to the specific surface area of the active material and the like. For example, from the viewpoint of maintaining excellent dispersion properties without impairing firm adhesion, it is preferably 28.0 MPa ^1/2 or less, and more preferably 26.5MPa ^1/2 or less.

The SP value of the monomer can be adjusted according to the type and number of polar groups introduced into the monomer.

The SP value of the monomer is the SP value of the monomer (homopolymer), which is determined by the Hoy method (refer to HL Hoy JOURNAL OF PAINT TECHNOLOGY Vol. 42, No. 541, 1970, 76-118, and POLYMER HANDBOOK 4 ^th , Chapter 59, VII 686 pages Table5, Table6 and Table6 in the following formula) conversion (for example, 1cal ^1/2 cm ^-3/2 ≈ 2.05J ^{1/ 2} cm ^-3/2 ≈ 2.05MPa ^1/2 ) Use it as SP value (MPa ^1/2 ).

[Formula 1]

B＝277

B=277

由下述式表示。In the formula, δ _t represents the SP value. F _t is a Molar attraction function (J×cm ³ ) ^1//2 /mol, which is represented by the following formula. V is a molar volume (cm ³ /mol) and is represented by the following formula.

It is represented by the following formula.

F _t =∑n _i F _{t, i} V=∑n _i V _i

In the above formula, F _t,i represents the molar attraction function of each structural unit, V _i represents the molar volume of each structural unit, Δ ^(p) _{T,i represents} the correction value of each structural unit, and ni represents the number of each structural unit. .

The polar group contained in the above-mentioned polar group-containing constituent is not particularly limited as long as the SP value of the monomer can be set to 19.0 MPa ^1/2 or more. Polar groups (hydroxyl group, carboxyl group, sulfonic acid group, phosphoric acid group, phosphonic acid group, amino group, etc.) of hydrogen (a hydrogen atom directly bonded to a heteroatom such as oxygen and nitrogen), a heterocyclic group, and a group containing an ether bond group (alkoxy group, polyoxy group, etc.), nitrile group, amide group, etc. Examples of the heterocyclic group include a group corresponding to the substituent T described later, and preferably a group composed of an aliphatic heterocyclic structure described in the following formula (M1). Among them, the polar group is preferably a polar group or a heterocyclic group containing active hydrogen from the viewpoint of improving the dispersion characteristics and adhesiveness and further improving the cycle characteristics.

In addition to proper adsorption of the active material by the polar group, the above-mentioned polar group-containing constituent is derived from a (meth)acrylic monomer or vinyl monomer from the viewpoint of diffusion into the dispersion medium. constituents.

The (meth)acrylic monomer includes a monomer having a (meth)acryloyloxy group or a (meth)acrylamido group, a (meth)acrylonitrile compound, and the like. The (meth)acrylic monomer is not particularly limited, and examples thereof include (meth)acrylic compounds, (meth)acrylate compounds, (meth)acrylamide compounds, and (meth)acrylonitrile compounds ( Among the meth)acrylic compounds (M), (meth)acrylate compounds are preferred. The (meth)acrylate compound is not particularly limited, and examples thereof include esters such as aliphatic or aromatic hydrocarbons or aliphatic or aromatic heterocyclic compounds, the number of carbon atoms of these hydrocarbons, heterocyclic compounds, and the like, and the types of hetero atoms. The number of or the number is not particularly limited, and can be appropriately set. For example, the number of carbon atoms can be set to 1 to 30.

The vinyl monomer is a vinyl-containing monomer other than the (meth)acrylic compound (M), and is not particularly limited, and examples thereof include vinyl-containing aromatic compounds (styrene compounds, vinyl naphthalenes) compounds, etc.), vinyl-containing heterocyclic compounds (vinylcarbazole compounds, vinylpyridine compounds, vinylimidazole compounds, vinyl-containing aromatic heterocyclic compounds such as N-vinylcaprolactam, etc., vinyl-containing non-aromatic compounds) aliphatic (aliphatic) heterocyclic compounds, etc.), allyl compounds, vinyl ether compounds, vinyl ketone compounds, vinyl ester compounds, dialkyl itaconic acid compounds, unsaturated carboxylic acid anhydrides and other vinyl compounds. As a vinyl compound, the "vinyl monomer" described in Unexamined-Japanese-Patent No. 2015-88486 is mentioned, for example.

The above-mentioned polar group-containing constituent is preferably a component derived from a (meth)acrylic monomer or vinyl monomer having the above-mentioned polar group. From the viewpoint of characteristics, it is more preferable to have a structure represented by the following formula (M1) or formula (M2).

[Chemical formula 2]

The structure represented by the above formula (M1) is a constituent having a heterocyclic group (wherein, when X is -NH-, it also corresponds to a constituent having a polar group including active hydrogen), and the above formula (M2) The shown structure is a constituent having a polar group containing active hydrogen.

In formula (M1) and formula (M2), atoms, substituents, linking groups and the like represented by the respective symbols are selected in an appropriate combination in consideration of the above SP values.

R, R ¹ , R ² and R ³ each represent a hydrogen atom or a substituent. The substituent which can be adopted as R, R ¹ , R ² or R ³ is not particularly limited, and examples of the substituent T described later include an alkyl group, an aryl group, a halogen atom, and the like. As R, R ¹ , R ² and R ³ , each is preferably a hydrogen atom, an alkyl group or a halogen atom, and more preferably a hydrogen atom, a methyl group or an ethyl group. More preferably, R ¹ and R ³ are hydrogen atoms, and R ² is a methyl group.

In formula (M1), L represents a linking group. The linking group that can be adopted as L can be appropriately selected from the following linking groups so that the structure represented by the formula (M1) becomes a structure derived from a (meth)acrylic monomer or a vinyl monomer. The linking group that can be used as L is more preferably a group containing a -CO-O- group or a -CO-N(R ^N )- group (R ^N is described below.), and particularly preferably -CO-O- Alkylene, or -CO-N(R ^N )-alkylene.

L ¹ and L ² each represent a single bond or a linking group, and preferably at least one of L ¹ and L ² is a linking group. The linking group that can be used as L ¹ and L ² can be appropriately selected from the following linking groups, and an alkylene group or an alkenylene group is preferable, and an alkylene group is more preferable.

X represents -O-, -S- or -NR ^M -, preferably -O-. ^RM represents a hydrogen atom or a substituent. The substituent which can be adopted as R ^M is not particularly limited, and the substituent T described later can be mentioned. R ^M is preferably a hydrogen atom or an alkyl group.

In formula (M1), the ring structure including L ¹ , L ² and X is not particularly limited as long as it is a structure in which L ¹ , L ² and X are appropriately combined. The ring structure of the heterocyclic group used by the polar group of the polar group-containing constituent is more preferably an aliphatic heterocyclic structure, still more preferably an aliphatic saturated heterocyclic structure, and particularly preferably a cyclic ether structure. The number of ring members of the above-mentioned ring structure in formula (M1) is not particularly limited, but is preferably a 3- to 10-membered ring, more preferably a 4- to 8-membered ring, and further preferably a 4- to 6-membered ring. As said ring structure in Formula (M1), an epoxy ring structure, an oxetane ring structure, a tetrahydrofuran ring structure, and a tetrahydropyran ring structure are mentioned preferably, for example.

In formula (M2), L ³ represents a single bond or a linking group. When a linking group is employed as L ³ , as the linking group, it may be appropriately selected from the following linking groups so that the structure represented by the formula (M2) becomes a (meth)acrylic monomer or vinyl monomer derived structure. The linking group that can be used as L ³ is more preferably a group containing a -CO-O- group or a -CO-N(R ^N )- group (R ^N is described below.), and particularly preferably -CO-O -Alkylene, or -CO-N(R ^N )-alkylene.

Z represents -OH or -COOH.

-Linker-

In the present invention, the linking group is not particularly limited, and examples thereof include an alkylene group (preferably 1 to 12 carbon atoms, more preferably 1 to 6, and even more preferably 1 to 3), an alkenylene group (carbon atoms) The number is preferably 2 to 6, more preferably 2 to 3), arylene group (preferably the number of carbon atoms is 6 to 24, more preferably 6 to 10), oxygen atom, sulfur atom, imino group (-NR ^N -: R ^N represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms.), a carbonyl group, a phosphoric acid linking group (-OP(OH)(O)-O-), a phosphonic acid linking group group (-P(OH)(O)-O-) or groups related to their combination, and the like. It is also possible to combine alkylene and oxygen atoms to form polyalkyleneoxy chains. The linking group is preferably a group formed by combining an alkylene group, an arylene group, a carbonyl group, an oxygen atom, a sulfur atom and an imino group, and more preferably an alkylene group, an arylene group, a carbonyl group, an oxygen atom and an imino group The group formed by combining amino groups is more preferably a group containing a -CO-O- group or a -CO-N(R ^N )- group (R ^N is as described above), and particularly preferably a -CO-O- group -CO-O-Alkylene.

In the present invention, the number of atoms constituting the linking group is preferably 1-36, more preferably 1-24, still more preferably 1-12. The number of linking atoms of the linking group is preferably 10 or less, and more preferably 8 or less. The lower limit is 1 or more. The above-mentioned number of linking atoms refers to the minimum number of atoms linking predetermined structural parts. For example, in the case of -CH ₂ -C(=O)-O-, the number of atoms constituting the linking group is 6, but the number of linking atoms is 3. The number of atoms constituting the linking group and the number of linking atoms are as described above, but the polyalkyleneoxy chain constituting the linking group is not limited to the above.

The above-mentioned linking groups may respectively have or not have a substituent. As a substituent which may have, for example, a substituent T is mentioned, and a halogen atom etc. are mentioned preferably.

Specific examples of monomers having an SP value of 19.0 MPa ^1/2 or more and constituents derived from the monomers include the following monomers and constituents M2 shown in Examples, but the present invention is not limited to to these.

Butyl acrylate (SP value 19.8MPa ^1/2 ), cyclohexyl methacrylate (SP value 19.0MPa ^1/2 ), glycidyl methacrylate (SP value 22.2MPa ^1/2 ), 2-hydroxyethyl acrylate Esters (SP value 25.9MPa ^1/2 ), glycerol monomethacrylate (SP value 26.2MPa ^1/2 ), methacrylic acid (SP value 19.0MPa ^1/2 ), succinic acid mono(2-acryloyloxy) Ethyl) ester (SP value 21.8MPa ^1/2 ), vinylimidazole (SP value 20.8MPa ^1/2 ), tetrahydrofurfuryl acrylate (SP value 21.4MPa ^1/2 ), methoxyethyl acrylate (SP value 20.9MPa ^1/2 ), ethyl acrylate (SP value 20.1MPa ^1/2 ), propyl acrylate (SP value 19.8MPa ^1/2 ), methyl methacrylate (SP value 19.4MPa 1/2 ), methyl methacrylate (SP value 19.4MPa 1/2 ), methyl methacrylate (SP value 19.4MPa ^1/2 ), methyl methacrylate Benzyl methacrylate (SP value 20.0MPa ^1/2 ), 2-(2-methoxyethoxy)ethyl methacrylate (SP value 20.4MPa ^1/2 ), Acrylonitrile (SP value 25.3MPa ^1/2 ) ² ), styrene (SP value 19.3MPa ^1/2 )

The binder-forming polymer preferably has at least a structural component derived from a styrene compound as the polar group-containing structural component, and more preferably has a structural component derived from a (meth)acrylic monomer and a source other than the styrene compound At least one of the constituent components derived from vinyl monomers, and the constituent components derived from a styrene compound (styrene constituent components).

The content rate of the above-mentioned polar group-containing constituent in the binder-forming polymer can be appropriately set according to the SP value, and is not particularly limited, and can also be set to 100 mol %, which is an important factor from the dispersion stability of the solid particles. From a viewpoint, it is preferably more than 0 mol % and 90 mol % or less, and more preferably more than 0 mol % and 85 mol % or less.

The content ratio _CA (mol %) of polar group-containing constituents other than styrene constituents in the binder-forming polymer (excluding constituents not having a polar group.) can be determined in consideration of the above range. It is appropriately set, preferably more than 0 mol % and 80 mol % or less, more preferably 0.1 to 60 mol %, still more preferably 1 to 40 mol %, particularly preferably 1 to 30 mol %, and most preferably 1 to 15 mol % %. Among the constituents containing polar groups, the content of constituents having no polar group (for example, constituents having the above-mentioned alkyl group) in the binder-forming polymer can be appropriately set, for example, it can be set to 0 to 90 mol%. On the other hand, the content ratio C _S (mol %) of the styrene constituent component in the binder-forming polymer can be appropriately set in consideration of the above range, and is preferably 20 to 90 mol %, more preferably 20 to 80 mol % %, more preferably 40 to 80 mol%, particularly preferably 70 to 80 mol%.

When the binder-forming polymer has two or more polar group-containing constituents including styrene constituents, from the viewpoints of dispersion stability, current collector adhesion, and cycle characteristics, the composition relative to styrene The molar ratio [C _A /C _S ] of the content ratio C _S (mol %) of the component to the content ratio C _A (mol %) of the other polar group-containing constituents is preferably 0.001 to 10, and more preferably It is 0.005-5, More preferably, it is 0.01-1.

The binder-forming polymer may have other components in addition to the above-mentioned polar group-containing components. The other constituents are not particularly limited as long as they can constitute the aforementioned polar group-containing constituents and copolymers, and examples thereof include constituents having an SP value of less than 19.0 MPa ^1/2 , and preferably a SP value of less than 1/2. 19.0 MPa ^1/2 of the constituents derived from (meth)acrylic monomers or vinyl monomers. These constituent components can be selected from the respective compounds described as monomers for deriving polar group-containing constituents, except that the SP values are different. Among them, alkyl (meth)acrylate compounds are preferred, and from the viewpoint of improving the solubility of the binder-forming polymer in the dispersion medium, the number of carbon atoms in the alkyl group constituting the alkyl ester is preferably 4 or more, and It is 6 or more, more preferably 8 or more, and still more preferably 10 or more. The upper limit is not particularly limited, but is preferably 20 or less, and more preferably 14 or less.

The content of other constituent components in the binder-forming polymer is not particularly limited, but is preferably 5 to 99 mol %, and more preferably 15 to 95 mol %.

When the binder-forming polymer does not have a styrene component as a polar group-containing component, the content of the other components is set in consideration of the above range, preferably 30 to 90 mol %, as the lower limit, 40 mol% or more is more preferable, 50 mol% or more is still more preferable, and 80 mol% or more is especially preferable. On the other hand, when a styrene constituent is included as a constituent including a polar group, the content of other constituents is appropriately set in consideration of the above-mentioned range, and is preferably 15 to 50 mol %, more preferably 15 to 40 mol %. The mol% is more preferably 15 to 30 mol%.

In addition, the molar ratio of the content of the polar group-containing constituent to the content of other constituents is not particularly limited as long as the above-mentioned content is satisfied, and can be appropriately set.

The type of the binder-forming polymer is not particularly limited as long as it has the above-mentioned polar group-containing constituent, and various known polymers can be used, and vinyl polymers and (meth)acrylic acid are preferably used. class of polymers.

Although it does not specifically limit as a vinyl polymer, For example, the polymer containing 50 mol% or more of vinyl monomers other than a (meth)acrylic-acid compound (M) is mentioned, for example. As a vinyl monomer, the said vinyl compound etc. are mentioned. The vinyl polymer includes polyvinyl alcohol, polyvinyl acetal, polyvinyl acetate, or a copolymer containing these.

The vinyl polymer may have a (meth)acrylic compound (M)-derived constituent that forms the (meth)acrylic polymer described later, in addition to the constituents derived from the vinyl monomer. The content rate of the constituent component derived from the vinyl monomer is preferably the same as the content ratio of the constituent component derived from the (meth)acrylic compound (M) in the (meth)acrylic polymer. The content of the constituent components derived from the (meth)acrylic compound (M) is not particularly limited as long as it is less than 50 mol % in the polymer, but is preferably 0 to 40 mol %, and more preferably 5 to 35 mol %.

Although it does not specifically limit as a (meth)acrylic-type polymer, For example, the polymer obtained by (co)polymerizing at least 1 type of the said (meth)acrylic compound (M) is preferable. Moreover, the (meth)acrylic-type polymer which consists of a copolymer of a (meth)acrylic compound (M) and another polymerizable compound (N) is also preferable. It does not specifically limit as another polymerizable compound (N), The said vinyl compound etc. are mentioned. The content rate of the other polymerizable compound (N) in the (meth)acrylic polymer is not particularly limited, but can be, for example, 50 mol % or less. As a (meth)acrylic-type polymer, the polymer described in Japanese Patent No. 6295332 is mentioned, for example.

The content rate of the structural component in a (meth)acrylic polymer is not specifically limited, It can select suitably, For example, it can be set to the following range. The content of the above-mentioned polar group-containing constituent is as described above.

The content rate in the (meth)acrylic polymer of the constituents derived from the (meth)acrylic compound (M) (including constituents having a polar group.) in the (meth)acrylic polymer is not particularly limited, and may be 100 mol. %. When the constituent component derived from the polymerizable compound (N) is contained, it is preferably 1 to 90 mol %, more preferably 10 to 80 mol %, still more preferably 20 to 70 mol %, and the lower limit is particularly preferably more than 50 mol %.

When the (meth)acrylic polymer contains a constituent derived from the polymerizable compound (N), the content of the constituent in the (meth)acrylic polymer is not particularly limited, but is preferably 1 mol % or more and 50 mol% or less, more preferably 10 mol% or more and 50 mol% or less, and particularly preferably 20 mol% or more and 50 mol% or less. 10 mol% can be used as an upper limit.

The binder-forming polymer may have substituents. The substituent is not particularly limited, but groups selected from the following substituents T are preferably used.

The binder-forming polymer can be synthesized by selecting a raw material compound (monomer) by a known method and polymerizing the raw material compound.

-Substituent T-

An alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, tert-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl (preferably alkenyl having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), alkynyl (preferably alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), cycloalkyl group (preferably, cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl group) , cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc., when it is an alkyl group in this specification, it usually means that a cycloalkyl group is included, but it is described separately here.), an aryl group (preferably a carbon number of 6 Aryl groups of ~26, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), aralkyl (preferably carbon atoms of 7- 23 aralkyl group, for example, benzyl, phenethyl, etc.), heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms, more preferably 5 having at least one oxygen atom, sulfur atom, nitrogen atom) Or a 6-membered ring heterocyclic group. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups. For example, tetrahydropyranyl, tetrahydrofuranyl, 2-pyridyl, 4-pyridyl, 2- imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, pyrrolidone, etc.), alkoxy (preferably an alkoxy having 1 to 20 carbon atoms, for example, methoxy, ethoxy group, isopropoxy group, benzyloxy group, etc.), aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthoxy, 3-methylphenoxy, 4 -Methoxyphenoxy and the like, when referred to as an aryloxy group in the present specification, means an aroyloxy group), a heterocyclic group (a group in which an -O- group is bonded to the above-mentioned heterocyclic group) ), alkoxycarbonyl (preferably an alkoxycarbonyl having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.), aryloxycarbonyl ( Preferably, aryloxycarbonyl having 6 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthoxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), heterocycle Oxycarbonyl group (a group formed by bonding -O-CO- group to the above-mentioned heterocyclic group), amino group (preferably including an amino group having 0 to 20 carbon atoms, an alkylamino group, an arylamino group, for example, an amino group (-NH _{2 )} ), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl (preferably sulfamoyl having 0 to 20 carbon atoms, for example, N , N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl (including alkylcarbonyl, alkenylcarbonyl, alkynylcarbonyl, arylcarbonyl, heterocyclic carbonyl, preferably with 1 to 20 carbon atoms) acyl, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonyl, benzoyl, naphthoyl, nicotinyl, etc.), acyloxy ( Including alkylcarbonyloxy, alkenylcarbonyloxy, alkynylcarbonyloxy, arylcarbonyloxy, heterocyclic carbonyloxy, preferably acyloxy having 1 to 20 carbon atoms, for example, ethyl Acyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonyloxy, benzoyloxy, naphthalene formyloxy, nicotinyloxy, etc.), aroyloxy (preferably aroyloxy having 7 to 23 carbon atoms, for example, benzoyloxy, etc.), carbamoyl (preferably having 1 to 23 carbon atoms) 20 carbamoyl group, for example, N,N-dimethylcarbamoyl group, N-phenylcarbamoyl group, etc.), amido group (preferably, amido group having 1 to 20 carbon atoms, for example, acetamido group, benzoyl group acylamino group, etc.), alkylthio group (preferably an alkylthio group having 1 to 20 carbon atoms, for example, methylthio group, ethylthio group, isopropylthio group, benzylthio group, etc.), arylthio group (preferably carbon number Arylthio groups of 6 to 26, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), heterocyclic thio (-S- group and the above-mentioned Heterocyclic group-bonded group), alkylsulfonyl (preferably an alkylsulfonyl group having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl (preferably carbon atoms Arylsulfonyl of 6 to 22, for example, benzenesulfonyl, etc.), alkylsilyl (preferably, alkylsilyl of 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl silyl group, trimethylsilyl group, triethylsilyl group, etc.), arylsilyl group (preferably an arylsilyl group having 6 to 42 carbon atoms, for example, triphenylsilyl group, etc.), alkane Oxysilyl group (preferably an alkoxysilyl group having 1 to 20 carbon atoms, for example, a monomethoxysilyl group, a dimethoxysilyl group, a trimethoxysilyl group, a triethoxysilyl group silyl group, etc.), aryloxysilyl group (preferably aryloxysilyl group with 6 to 42 carbon atoms, for example, triphenoxysilyl group, etc.), phosphoryl group (preferably with 0 to 4 carbon atoms) 20 phosphoric acid group, for example, -OP(=O)(R ^P ) ₂ ), phosphono group (preferably a phosphono group having 0 to 20 carbon atoms, for example, -P(=O)(R ^P ) ₂ ), oxygen Phosphine group (preferably a phosphine group having 0 to 20 carbon atoms, for example, -P(R ^P ) ₂ ), phosphonic acid group (preferably a phosphonic acid group having 0 to 20 carbon atoms, for example, -PO(OR ^P ) ₂ ), sulfo group (sulfonic acid group, -SO ₃ R ^P ), carboxyl group, hydroxyl group, sulfanyl group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). R ^P is a hydrogen atom or a substituent (preferably a group selected from the substituent T).

Also, each of the groups listed in these substituents T may be further substituted with the above-mentioned substituents T.

The above-mentioned alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group, and/or alkynylene group, etc. may be cyclic or chain, and may be linear or branched.

(Physical properties or properties of polymer binders or binder-forming polymers, etc.)

The above-mentioned polymer binder or binder-forming polymer preferably has the following physical properties, characteristics, and the like.

The SP value (unit: MPa ^1/2 ) of the binder-forming polymer is not particularly limited, but from the viewpoint of the dispersion stability of the solid particles, for example, it is preferably 17.0 to 22.0, more preferably 17.5 to 21.0, and even more preferably 18.0 to 20.0. The SP value of the binder-forming polymer can be adjusted according to the type, content rate, and the like of the above-mentioned constituent components.

The SP value of each constituent component was obtained as described above, and the SP value of the binder-forming polymer was calculated from the following formula. In addition, the SP value of the structural component calculated|required by the said literature was converted into SP value (MPa ^1/2 ), and used.

SP _p ² =(SP ₁ ² ×W ₁ )+(SP ₂ ² ×W ₂ )+…

In the formula, SP ₁ , SP ₂ . . . represent the SP values of the constituent components, and W ₁ , W ₂ . . . represent the mass fractions of the constituent components.

In the present invention, the mass fraction of a constituent is the mass fraction in the binder-forming polymer of the constituent (the raw material compound into which the constituent is introduced).

The water concentration of the polymer binder (polymer) is preferably 100 ppm (mass basis) or less. In addition, the polymer binder may crystallize and dry the polymer, or the polymer binder dispersion liquid may be used as it is.

The binder-forming polymer is preferably amorphous. In the present invention, a polymer being "amorphous" typically means that no endothermic peak due to crystal melting is observed when measured at the glass transition temperature.

The binder-forming polymer may be a non-crosslinked polymer or a crosslinked polymer. In addition, when the polymer is cross-linked by heating or applying a voltage, the molecular weight may be larger than the above-mentioned molecular weight. It is preferable that the mass-average molecular weight of the polymer is in the range described later when the use of the all-solid-state secondary battery is started.

The mass average molecular weight of the binder-forming polymer is not particularly limited. For example, 15,000 or more are preferable, 30,000 or more are more preferable, and 50,000 or more are still more preferable. The upper limit is actually 5,000,000 or less, preferably 4,000,000 or less, more preferably 3,000,000 or less, and still more preferably 1,000,000 or less.

-Determination of molecular weight-

In the present invention, the molecular weight of a polymer such as a polymer and a polymer chain refers to a mass average molecular weight in terms of standard polystyrene obtained by gel permeation chromatography (GPC) unless it is particularly limited. As the measurement method, the following conditions 1 or 2 (priority) methods can basically be mentioned. Among them, an appropriate eluent may be appropriately selected and used according to the type of polymer.

(Condition 1)

Column: Connect two TOSOH TSKgel Super AWM-H (trade name, manufactured by TOSOH CORPORATION)

Carrier: 10mM LiBr/N-methylpyrrolidone

Measurement temperature: 40℃

Carrier flow: 1.0ml/min

Sample concentration: 0.1 mass%

Detector: RI (Refractive Index) detector

(Condition 2)

Column: A column to which TOSOH TSKgel Super HZM-H, TOSOH TSKgel Super HZ4000, and TOSOH TSKgel Super HZ2000 (all trade names, manufactured by Tosoh Corporation) were connected was used.

Carrier: Tetrahydrofuran

Measurement temperature: 40℃

Carrier flow: 1.0ml/min

Sample concentration: 0.1 mass%

Detector: RI (Refractive Index) detector

The electrode composition of the present invention may contain one type of polymer binder, or may contain two or more types.

The content of the polymer binder in the electrode composition is not particularly limited, but from the viewpoints of dispersion stability, current collector adhesion and cycle characteristics, it is preferably 0.1 to 10.0 mass % in 100 mass % of solid content, More preferably, it is 0.2-8 mass %, More preferably, it is 0.3-6 mass %, Especially preferably, it is 0.5-3 mass %.

In the present invention, in 100% by mass of the solid content, the mass ratio of the total mass (total amount) of the sulfide-based inorganic solid electrolyte and the active material to the total mass of the polymer binder [(the sulfide-based inorganic solid electrolyte mass+mass of active material)/(total mass of polymer binder)] is preferably in the range of 1,000 to 1. Moreover, it is more preferable that this ratio is 500-2, and it is still more preferable that it is 100-10.

<Dispersion medium>

The electrode composition of the present invention contains a dispersion medium for dispersing or dissolving the above-mentioned components.

The dispersion medium may be any organic compound that exhibits a liquid state in the environment of use, and examples thereof include various organic solvents, and specific examples thereof include alcohol compounds, ether compounds, amide compounds, amine compounds, ketone compounds, and aromatic compounds. Aliphatic compounds, aliphatic compounds, nitrile compounds, ester compounds, etc.

The dispersion medium may be a nonpolar dispersion medium (hydrophobic dispersion medium) or a polar dispersion medium (hydrophilic dispersion medium), but is preferably a nonpolar dispersion medium from the viewpoint of being able to express excellent dispersibility. The non-polar dispersion medium generally refers to a property with low affinity for water, but in the present invention, for example, ester compounds, ketone compounds, ether compounds, aromatic compounds, aliphatic compounds and the like can be mentioned.

Examples of alcohol compounds include methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, ethylene glycol, propylene glycol, glycerin, 1,6-hexanediol, cyclohexanediol, and sorbose. Alcohol, xylitol, 2-methyl-2,4-pentanediol, 1,3-butanediol, 1,4-butanediol.

Examples of ether compounds include alkylene glycols (diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, etc.), alkylene glycol monoalkyl ethers (ethylene glycol monomethyl ether, etc.) , ethylene glycol monobutyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, etc.), alkylene glycol dioxane base ethers (ethylene glycol dimethyl ether, etc.), dialkyl ethers (dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, etc.), cyclic ethers (tetrahydrofuran, dioxane (including 1,2 -, 1,3- and 1,4- isomers) etc.).

Examples of the amide compound include N,N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, Formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropanamide, hexamethylphosphoric triamide, etc.

As an amine compound, triethylamine, diisopropylethylamine, tri-n-butylamine, etc. are mentioned, for example.

Examples of the ketone compound include acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclopentanone, cyclohexanone, cycloheptanone, dipropyl ketone, dibutyl ketone, and diisobutyl ketone. Propyl ketone (DIPK), diisobutyl ketone (DIBK), isobutyl propyl ketone, sec-butyl propyl ketone, amyl propyl ketone, butyl propyl ketone, etc.

As an aromatic compound, benzene, toluene, xylene, etc. are mentioned, for example.

Examples of the aliphatic compound include hexane, heptane, octane, nonane, decane, dodecane, cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and cyclooctane. , Decalin, paraffin, gasoline, naphtha, kerosene, light oil, etc.

As a nitrile compound, acetonitrile, propionitrile, isobutyronitrile, etc. are mentioned, for example.

Examples of the ester compound include ethyl acetate, butyl acetate, propyl acetate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, butyl valerate, and isobutyric acid. Ethyl, propyl isobutyrate, isopropyl isobutyrate, isobutyl isobutyrate, propyl pivalate, isopropyl pivalate, butyl pivalate, isobutyl pivalate, etc.

In the present invention, among them, ether compounds, ketone compounds, aromatic compounds, aliphatic compounds, and ester compounds are preferable, and ester compounds, ketone compounds, or ether compounds are more preferable.

The number of carbon atoms of the compound constituting the dispersion medium is not particularly limited, but is preferably 2 to 30, more preferably 4 to 20, still more preferably 6 to 15, and particularly preferably 7 to 12.

The dispersion medium preferably has an SP value (unit: MPa ^1/2 ) of 14 to 24, more preferably 15 to 22, and even more preferably 16 to 20, from the viewpoint of the dispersion stability of solid particles. The difference (absolute value) of the SP value of the dispersion medium and the polymer binder is not particularly limited, and the molecular chain of the polymer forming the polymer binder in the dispersion medium is extended to improve its own dispersibility, thereby enabling further From the viewpoint of improving the dispersion stability of the solid particles, it is preferably 3 or less, more preferably 0 to 2, and even more preferably 0 to 1. Regarding the difference (absolute value) of the above SP value, when the electrode composition of the present invention contains two or more kinds of binders, preferably at least one binder satisfies the difference (absolute value) of the above SP value, and all the binders It is also one of the preferable modes to satisfy the difference (absolute value) of the SP value.

The SP value of the dispersion medium is a value obtained by converting the SP value calculated by the above Hoy method into a unit of MPa ^1/2 . When the electrode composition contains two or more kinds of dispersion medium, the SP value of the dispersion medium refers to the SP value of the entire dispersion medium, and is set as the sum of the products of the SP value of each dispersion medium and the mass fraction. Specifically, it is calculated in the same manner as the calculation method of the SP value of the polymer described above, except that the SP value of each dispersion medium is used instead of the SP value of the constituent components.

The SP values (units omitted) of the dispersion medium are shown below.

MIBK (18.4), diisopropyl ether (16.8), dibutyl ether (17.9), diisobutyl ketone (17.9), DIBK (17.9), butyl butyrate (18.6), butyl acetate (18.9), toluene (18.5), ethylcyclohexane (17.1), cyclooctane (18.8), isobutyl ether (15.3), N-methylpyrrolidone (NMP, 25.4)

The boiling point of the dispersion medium under normal pressure (1 atmospheric pressure) is preferably 50°C or higher, and more preferably 70°C or higher. The upper limit is preferably 250°C or lower, more preferably 220°C or lower.

The electrode composition of the present invention only needs to contain one type of dispersion medium, and may contain two or more types.

In the present invention, the content of the dispersion medium in the electrode composition is not particularly limited, and can be appropriately set. For example, in an electrode composition, 20-80 mass % is preferable, 30-70 mass % is more preferable, and 40-60 mass % is especially preferable.

＜Conductive additives＞

The electrode composition of the present invention preferably contains a conductive aid, for example, a silicon element-containing active material as a negative electrode active material is preferably used together with a conductive aid.

There is no restriction|limiting in particular as a conductive auxiliary agent, The conductive auxiliary agent known as a general conductive auxiliary agent can be used. For example, as electron conductive materials, graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, Ketjen black, and furnace black, amorphous carbons such as needle coke, vapor-grown carbon fibers, or Carbon fibers such as carbon nanotubes, carbonaceous materials such as graphene or fullerene, metal powders such as copper and nickel, metal fibers, and derivatives of polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene Conductive polymers such as materials.

In the present invention, when an active material and a conductive assistant are used in combination, among the above-mentioned conductive assistants, ions of metals belonging to Group 1 or Group 2 of the periodic table are not generated when charging and discharging the battery (preferably intercalation and deintercalation of Li ions), and as a conductive aid that does not function as an active material. Therefore, among the conductive assistants, those that can function as active materials in the active material layer are classified as active materials, not conductive assistants, when the battery is charged and discharged. Whether or not it functions as an active material when charging and discharging a battery is determined by the combination with the active material, not uniformly.

The electrode composition of the present invention may contain one type of conductive aid or two or more types.

The shape of the conductive aid is not particularly limited, but it is preferably in the form of particles. The average particle diameter at this time is not particularly limited, and can be appropriately set. In addition, the specific surface area usually has a smaller value than the specific surface area of the active material described later, but is not limited to this, and can be appropriately set.

When the electrode composition of the present invention contains a conductive aid, the content of the conductive aid in the electrode composition is preferably 0 to 10% by mass in 100% by mass of solid content.

<Inorganic solid electrolytes other than sulfide-based inorganic solid electrolytes>

The electrode composition of the present invention may contain inorganic solid electrolytes other than sulfide-based inorganic solid electrolytes. For example, oxide-based sulfide-based inorganic solid electrolytes, halide-based sulfide-based inorganic solid electrolytes, and hydride-based inorganic solid electrolytes commonly used in all-solid-state secondary batteries may be mentioned. The content of the inorganic solid electrolyte other than the sulfide-based inorganic solid electrolyte in the electrode composition is not particularly limited, and can be appropriately set within a range that does not impair the effects of the present invention.

＜Lithium salt＞

The electrode composition of the present invention preferably further contains a lithium salt (supporting electrolyte).

The lithium salt is preferably a lithium salt commonly used for such products, and is not particularly limited. For example, the lithium salts described in paragraphs 0082 to 0085 of Japanese Patent Laid-Open No. 2015-088486 are preferred.

When the electrode composition of the present invention contains a lithium salt, the content of the lithium salt is preferably 0.1 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the solid electrolyte. The upper limit is preferably 50 parts by mass or less, and more preferably 20 parts by mass or less.

＜Dispersant＞

Since the above-mentioned polymer binder functions as a dispersant, the electrode composition of the present invention may not contain a dispersant other than the polymer binder, or may contain a dispersant. As the dispersant, a dispersant generally used for all-solid-state secondary batteries can be appropriately selected and used. Generally, the desired compounds in particle adsorption, steric repulsion and/or electrostatic repulsion are suitably used.

＜Other additives＞

The electrode composition of the present invention can appropriately contain an ionic liquid, a thickener, a crosslinking agent (substances that undergo a crosslinking reaction by radical polymerization, polycondensation, or ring-opening polymerization, etc.), a polymerization initiator (acid generated by heat or light, etc.) or radical substances, etc.), defoaming agent, leveling agent, dehydrating agent, antioxidant, etc. as other components other than the above-mentioned components. The ionic liquid is a liquid contained in order to further improve the ionic conductivity, and known liquids can be used without particular limitation. In addition, a polymer other than the polymer forming the above-mentioned polymer binder may contain a commonly used binder or the like.

(Preparation of Electrode Composition)

In the electrode composition of the present invention, a sulfide-based inorganic solid electrolyte, a polymer binder, an active material and a dispersion medium, a conductive auxiliary agent, an appropriate lithium salt, and any other components are mixed, for example, in various commonly used mixers. Mix. Therefore, it is preferable to prepare a slurry as a mixture.

The mixing method is not particularly limited, and may be mixed at one time or sequentially. The environment for mixing is not particularly limited, and examples thereof include under dry air, under inert gas, and the like.

[Electrode Sheets for All-Solid-State Secondary Batteries]

The electrode sheet for an all-solid-state secondary battery of the present invention (it may also be simply referred to as an electrode sheet.) is a sheet-like molded body capable of forming an electrode (laminated body of an active material layer and a current collector) of an all-solid-state secondary battery. There are various ways of use.

The electrode sheet of the present invention has an active material layer composed of the electrode composition of the present invention described above on the surface of the current collector. Therefore, the active material layer and the current collector are tightly adhered (the current collector adhesion is strong), and even the solid particles are firmly adhered to each other, and the active material layer exhibits high strength. Even if the electrode sheet is wound around a core by an industrial manufacturing method such as a highly productive roll-to-roll method or during or after the manufacturing process, the active material layer and the current collector can be maintained in close contact. In addition, the occurrence of defects (chips, cracks, cracks, peeling, etc.) in the active material layer can also be suppressed. By being used as an electrode (a laminate of an active material layer and a current collector) of an all-solid-state secondary battery, the electrode sheet can impart excellent cycle characteristics to an all-solid-state secondary battery.

The electrode sheet of the present invention may be any electrode sheet having an active material layer on the surface of the current collector. In addition, the electrode sheet also includes a form having a current collector, an active material layer, and a solid electrolyte layer in this order, and a form having a current collector, an active material layer, a solid electrolyte layer, and an active material layer in this order. The electrode sheet may have other layers in addition to the above-mentioned layers. As another layer, a protective layer (release sheet), a current collector, a coating layer, etc. are mentioned, for example.

The base material is not particularly limited as long as it can support the active material layer, and examples thereof include the materials described in the current collector described later, sheet bodies (plate bodies) such as organic materials and inorganic materials, and the like. . As an organic material, various polymers etc. are mentioned, Specifically, polyethylene terephthalate, polypropylene, polyethylene, cellulose, etc. are mentioned. As an inorganic material, glass, a ceramic, etc. are mentioned, for example.

The active material layer provided on the surface of the current collector is formed of the electrode composition of the present invention. In the active material layer formed from the electrode composition of the present invention, the content of each component is not particularly limited, but preferably has the same meaning as the content of each component in the solid content of the electrode composition of the present invention. The layer thickness of each layer constituting the electrode sheet of the present invention is the same as the layer thickness of each layer described in the all-solid-state secondary battery described later.

In the present invention, each layer constituting the electrode sheet for an all-solid-state secondary battery may have a single-layer structure or a multilayer structure.

In addition, constituent layers, such as a solid electrolyte layer, are formed from common materials.

[Manufacturing method of electrode sheet for all-solid-state secondary battery]

The method for producing the electrode sheet for an all-solid-state secondary battery of the present invention is not particularly limited, and it can be produced by forming an active material layer on the surface of a current collector using the electrode composition of the present invention. For example, a method of forming a film (coating and drying) of the electrode composition of the present invention on the surface of a current collector (substrate) to form a layer (coating and drying layer) of the electrode composition is preferably used. Thereby, a sheet having the current collector and the coating dry layer can be produced. Here, the coating-dried layer refers to a layer formed by coating the electrode composition of the present invention and drying the dispersion medium (that is, formed using the electrode composition of the present invention, and formed from the electrode composition of the present invention) layer formed by removing the composition of the dispersion medium). The dispersion medium may remain in the coating dry layer or the active material layer composed of the coating dry layer within a range that does not impair the effects of the present invention, and the residual amount can be, for example, 3 mass % or less in each layer. The coated dry layer contains a polymeric binder as described above.

In the manufacturing method of the electrode sheet for all-solid-state secondary batteries of this invention, each process of coating, drying, etc. is demonstrated in the following manufacturing method of an all-solid-state secondary battery.

In the above-mentioned preferred method, when the electrode composition of the present invention is formed on a current collector to form an electrode sheet for an all-solid-state secondary battery, the adhesion between the current collector and the active material layer can be made strong. .

In the manufacturing method of the electrode sheet for all-solid-state secondary batteries of this invention, it is also possible to pressurize the coating dry layer. The pressurizing conditions and the like will be described in the method of manufacturing an all-solid-state secondary battery to be described later.

The obtained coating dry layer becomes an active material layer by appropriately performing a pressure treatment or the like.

Moreover, in the manufacturing method of the electrode sheet for all-solid-state secondary batteries of this invention, a base material, a protective layer (especially a peeling sheet), etc. can also be peeled.

The method for producing an electrode sheet for an all-solid-state secondary battery of the present invention can be applied to an industrial production method such as a highly productive roll-to-roll method by using the electrode composition of the present invention, and can also be applied to a production process or a The method of winding up on a core after production enables production of electrode sheets for all-solid-state secondary batteries with high productivity.

[All-solid-state secondary battery]

The all-solid-state secondary battery of the present invention has a positive electrode active material layer, a negative electrode active material layer facing the positive electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The positive electrode active material layer is preferably formed on the positive electrode current collector, and constitutes the positive electrode. The negative electrode active material layer is preferably formed on the negative electrode current collector, and constitutes the negative electrode.

At least one of the negative electrode active material layer and the positive electrode active material layer is formed from the electrode composition of the present invention, and the negative electrode active material layer and the positive electrode active material layer are formed from the electrode composition of the present invention. In the present invention, the active material layer of an all-solid-state secondary battery formed from the electrode composition of the present invention includes an electrode sheet for an all-solid-state secondary battery of the present invention (which has an active material layer and a collector formed from the electrode composition of the present invention). In the case of layers other than the electric body, a sheet obtained by removing these layers) forms a layered body (electrode) of an active material layer and a current collector. It is preferable that the active material layer formed from the electrode composition of the present invention is the same as that in the solid content of the electrode composition of the present invention as to the kind and content of the components to be contained. In addition, when the active material layer or the solid electrolyte layer is not formed of the electrode composition of the present invention, a known material can be used.

The all-solid-state secondary battery of the present invention exhibits excellent cycle characteristics, and can perform high-speed charge and discharge under a large current in addition to charge and discharge under normal conditions. In addition, it exhibits low resistance and high ionic conductivity, and can extract a large current.

The respective thicknesses of the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer are not particularly limited. Considering the size of a general all-solid-state secondary battery, the thickness of each layer is preferably 10 to 1,000 μm, and more preferably 20 μm or more and less than 500 μm. In the all-solid-state secondary battery of the present invention, the thickness of at least one of the positive electrode active material layer and the negative electrode active material layer is more preferably 50 μm or more and less than 500 μm.

＜Frame＞

The all-solid-state secondary battery of the present invention can be used as an all-solid-state secondary battery in the state of the above-described structure depending on the application, but it is preferably further enclosed in a suitable case for use in order to make it a dry battery. The case may be a metallic case or a resin (plastic) case. When a metallic case is used, for example, an aluminum alloy or a case made of stainless steel can be used. Preferably, the metallic case is divided into a positive electrode side case and a negative electrode side case and is electrically connected to the positive electrode current collector and the negative electrode current collector, respectively. It is preferable that the case on the positive electrode side and the case on the negative electrode side are joined and integrated with a short-circuit preventing gasket therebetween.

Hereinafter, an all-solid-state secondary battery according to a preferred embodiment of the present invention will be described with reference to FIG. 1 , but the present invention is not limited thereto.

FIG. 1 is a cross-sectional view schematically showing an all-solid-state secondary battery (lithium ion secondary battery) according to a preferred embodiment of the present invention. The all-solid-state secondary battery 10 of this embodiment includes a negative electrode current collector 1 , a negative electrode active material layer 2 , a solid electrolyte layer 3 , a positive electrode active material layer 4 , and a positive electrode current collector 5 in this order when viewed from the negative electrode side. Each layer is in contact with each other and is adjacent to each other. By adopting such a structure, electrons (e ⁻ ) are supplied to the negative electrode side during charging, and lithium ions (Li ⁺ ) are accumulated there. On the other hand, during discharge, the lithium ions (Li ⁺ ) accumulated in the negative electrode are returned to the positive electrode side, and electrons are supplied to the working site 6 . In the example shown in the figure, a light bulb is used as a model at the work site 6, and the light bulb is lit by discharge. This all-solid-state secondary battery 10 exhibits the above-mentioned excellent characteristics.

When an all-solid-state secondary battery having the layer structure shown in FIG. 1 is placed in a 2032-type coin-type battery case, the all-solid-state secondary battery is sometimes referred to as a laminate for an all-solid-state secondary battery, and the A battery (for example, the button-type all-solid-state secondary battery 13 shown in FIG. 2 ) produced by placing the laminate for an all-solid-state secondary battery in a 2032-type button battery case is called an all-solid-state secondary battery.

(Positive electrode active material layer, solid electrolyte layer, negative electrode active material layer)

In the all-solid-state secondary battery 10, the positive electrode active material layer and the negative electrode active material layer are formed from the electrode composition of the present invention. In other words, the positive electrode formed by laminating the positive electrode active material layer and the positive electrode current collector and the negative electrode formed by laminating the negative electrode active material layer and the negative electrode current collector are formed of the electrode sheet of the present invention.

The sulfide-based inorganic solid electrolyte and polymer binder contained in the positive electrode active material layer 4 and the negative electrode active material layer 2 may be of the same type or different types, respectively. The ratio of the positive electrode active material to the negative electrode active material may be different. The surface areas can be the same or different.

In the all-solid-state secondary battery 10 , the negative electrode active material layer can be a lithium metal layer. As the lithium metal layer, a layer formed by depositing or molding lithium metal powder, a lithium foil, a lithium vapor-deposited film, and the like can be mentioned. The thickness of the lithium metal layer can be set to, for example, 1 to 500 μm regardless of the thickness of the negative electrode active material layer.

The positive electrode current collector 5 and the negative electrode current collector 1 are preferably electron conductors.

In the present invention, either one of the positive electrode current collector and the negative electrode current collector, or a combination of both may be simply referred to as a current collector.

As the material for forming the positive electrode current collector, in addition to aluminum, aluminum alloy, stainless steel, nickel, titanium, etc., a material obtained by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver (a material in which a thin film is formed) is preferable, wherein , more preferably aluminum and aluminum alloys.

As the material for forming the negative electrode current collector, in addition to aluminum, copper, copper alloy, stainless steel, nickel, titanium, etc., carbon, nickel, titanium, or silver is preferably treated on the surface of aluminum, copper, copper alloy, or stainless steel. Preferred are aluminum, copper, copper alloys and stainless steel.

The shape of the current collector is usually a membrane-like shape, but a mesh, a perforated body, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like can also be used.

The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm. Furthermore, it is also preferable to provide unevenness on the surface of the current collector by surface treatment.

In the all-solid-state secondary battery 10 , layers formed of known materials can also be applied to the solid electrolyte layer and the active material layer.

In the present invention, functional layers, members, etc. may be appropriately inserted or arranged between the layers of the negative electrode current collector, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, and the positive electrode current collector or on the outside thereof. . In addition, each layer may be configured as a single layer or may be configured as a multilayer.

[Manufacture of all-solid-state secondary battery]

All-solid-state secondary batteries can be manufactured by conventional methods. Specifically, an all-solid-state secondary battery can be produced by forming at least one active material layer using the electrode composition or the like of the present invention, or forming at least one electrode using the electrode sheet of the present invention, and forming a solid electrolyte using a known material. layer, another active material layer or electrode as appropriate.

The all-solid-state secondary battery of the present invention can be carried out by a method including (via) a step of applying the electrode composition of the present invention on the surface of a current collector and drying to form a coating film (film formation). Method for manufacturing an electrode sheet for an all-solid-state secondary battery).

For example, an electrode composition containing a positive electrode active material as a positive electrode material (positive electrode composition) is formed on a metal foil as a positive electrode current collector to form a positive electrode active material layer to produce a positive electrode sheet for an all-solid-state secondary battery. Next, the solid electrolyte layer is formed by film-forming the solid electrolyte composition for forming the solid electrolyte layer on the positive electrode active material layer. Further, the negative electrode active material layer is formed by forming a film of an electrode composition containing a negative electrode active material as a negative electrode material (negative electrode composition) on the solid electrolyte layer. By stacking the negative electrode current collector (metal foil) on the negative electrode active material layer, an all-solid-state secondary battery having a structure in which the solid electrolyte layer is sandwiched between the positive electrode active material layer and the negative electrode active material layer can be obtained. It can also be enclosed in a case and used as a desired all-solid-state secondary battery.

In addition, contrary to the method of forming each layer, an all-solid-state secondary battery can also be produced by forming a negative electrode active material layer, a solid electrolyte layer, and a positive electrode active material layer on a negative electrode current collector and stacking the positive electrode current collector.

As another method, the following method can be mentioned. That is, the positive electrode sheet for all-solid-state secondary batteries was produced as mentioned above. Then, an electrode composition containing a negative electrode active material as a negative electrode material (negative electrode composition) was formed into a film on a metal foil as a negative electrode current collector to form a negative electrode active material layer to produce a negative electrode sheet for an all-solid-state secondary battery. Next, on the active material layer of any one of these sheets, a solid electrolyte layer was formed as described above. Then, on the solid electrolyte layer, the other of the positive electrode sheet for an all-solid-state secondary battery and the negative electrode sheet for an all-solid-state secondary battery is laminated so that the solid electrolyte layer and the active material layer are in contact with each other. In this way, an all-solid-state secondary battery can be manufactured.

In addition, as another method, the following method is mentioned. That is, the positive electrode sheet for all-solid-state secondary batteries and the negative electrode sheet for all-solid-state secondary batteries were produced as described above. In addition, a solid electrolyte sheet for an all-solid-state secondary battery composed of a solid electrolyte layer was produced by forming a film of the electrode composition on a substrate. And it laminated|stacked so that the solid electrolyte layer peeled from the base material was sandwiched by the positive electrode sheet for all-solid-state secondary batteries and the negative electrode sheet for all-solid-state secondary batteries. In this way, an all-solid-state secondary battery can be manufactured.

Furthermore, as described above, the positive electrode sheet for all-solid-state secondary batteries, the negative-electrode sheet for all-solid-state secondary batteries, and the solid electrolyte sheet for all-solid-state secondary batteries were produced. Next, in a state where the positive electrode active material layer or the negative electrode active material layer is in contact with the solid electrolyte layer, the positive electrode sheet for an all-solid-state secondary battery or the negative electrode sheet for an all-solid-state secondary battery and the solid electrolyte sheet for an all-solid-state secondary battery are stacked and Pressurize. In this way, the solid electrolyte layer is transferred to the positive electrode sheet for all-solid-state secondary batteries or the negative-electrode sheet for all-solid-state secondary batteries. Then, the solid electrolyte layer obtained by peeling the base material of the solid electrolyte sheet for all-solid-state secondary batteries and the negative electrode sheet for all-solid-state secondary batteries or the positive electrode sheet for all-solid-state secondary batteries (after the negative electrode active material layer or the positive electrode is activated The substance layer and the solid electrolyte layer are in contact with each other) and are superimposed and pressurized. In this way, an all-solid-state secondary battery can be manufactured. The pressurizing method, pressurizing conditions, etc. in this method are not particularly limited, and the methods, pressurizing conditions, and the like described in the pressurizing of the composition to be applied later can be applied.

The solid electrolyte layer or the like is formed by, for example, press-molding a sulfide-based inorganic solid electrolyte or a solid electrolyte composition or the like on a substrate or an active material layer under pressure conditions described later.

In the above-mentioned production method, the electrode composition of the present invention is used in the electrode composition (at least one of the negative electrode composition and the positive electrode composition) for forming a film on the surface of the current collector.

When an active material layer is formed from an electrode composition other than the electrode composition of the present invention, or when a solid electrolyte layer is formed, generally used compositions and the like can be mentioned as these materials. In addition, in each of the above-described production methods, a lithium metal layer can also be used as a negative electrode (a laminate of a negative electrode active material layer and a negative electrode current collector). In addition, the negative electrode active material layer is not formed during the manufacture of the all-solid-state secondary battery, and the metal belonging to the first or second group of the periodic table is accumulated in the negative electrode current collector by initializing or charging to be described later. The ions and electrons are combined and deposited on the negative electrode current collector or the like as a metal, whereby the negative electrode active material layer can also be formed.

<Formation of each layer (film formation)>

The coating method in particular of the electrode composition etc. of this invention is not restrict|limited, It can select suitably. For example, coating (preferably wet coating), spray coating, spin coating, dip coating, slit coating, stripe coating, and bar coating are mentioned.

The coated composition is preferably subjected to drying treatment (heat treatment). The drying treatment may be performed after applying the electrode composition separately, or may be performed after the multi-layer coating. The drying temperature is not particularly limited, but for example, it is preferably 30°C or higher, more preferably 60°C or higher, and further preferably 80°C or higher. The upper limit is not particularly limited. For example, from the viewpoint of preventing damage to each component of the all-solid-state secondary battery, it is preferably 300°C or lower, more preferably 250°C or lower, and further preferably 200°C or lower.

It is preferable to pressurize each layer or the all-solid-state secondary battery after coating the composition, after stacking the constituent layers, or after fabricating the all-solid-state secondary battery. As a pressurizing method, a hydraulic cylinder press etc. are mentioned. Although it does not specifically limit as a pressurization pressure, Usually, it is preferable to be in the range of 5-1500 MPa.

Also, the coated electrode composition may be heated while being pressurized. Although it does not specifically limit as a heating temperature, Generally, it is the range of 30-300 degreeC. Pressing can also be performed at a temperature higher than the glass transition temperature of the sulfide-based inorganic solid electrolyte. In addition, stamping can also be performed at a temperature higher than the glass transition temperature of the binder-forming polymer. Typically, however, it is a temperature that does not exceed the melting point of the polymer.

Pressurization may be performed in a state where the dispersion medium is preliminarily dried, or may be pressurized in a state where the dispersion medium remains.

In addition, the respective compositions may be applied simultaneously, or the application, drying, and punching may be performed simultaneously and/or stepwise. After coating on the respective substrates, lamination can be performed by transfer.

As the production process, for example, during coating, the environment during heating or pressurization is not particularly limited, and can be under atmospheric pressure, under dry air (dew point -20°C or lower), under inert gas (for example, under argon gas) , helium, nitrogen) in any environment.

The punching time may apply high pressure over a short period of time (eg, within a few hours), or may apply a moderate degree of pressure over a long period of time (more than 1 day). In addition to the electrode sheet for an all-solid-state secondary battery, for example, in the case of an all-solid-state secondary battery, a restraint tool (screw tightening pressure, etc.) of the all-solid-state secondary battery can be used to continuously apply moderate pressure.

The punching pressure may be a uniform pressure or a different pressure relative to the pressure-receiving portion such as the sheet surface.

The pressing pressure can be changed according to the area or film thickness of the pressure-receiving portion. In addition, it is also possible to change the pressure in stages for the same portion.

The stamping surface can be smooth or rough.

<Initialization>

The all-solid-state secondary battery manufactured as described above is preferably initialized after manufacture or before use. The initialization is not particularly limited. For example, initial charge and discharge can be performed in a state where the pressing pressure is increased, and then the pressure can be released until it reaches the general operating pressure of an all-solid-state secondary battery.

The method for producing an all-solid-state secondary battery of the present invention can be applied to an industrial production method such as a highly productive roll-to-roll method by using the electrode composition of the present invention, and can also be applied to a roll during the production process or after production The manufacturing method of the winding core, and the all-solid-state secondary battery that realizes the above-mentioned excellent battery performance can be manufactured with high productivity.

[Use of all-solid-state secondary battery]

The all-solid-state secondary battery of the present invention can be applied to various applications. The applicable form is not particularly limited. For example, when it is mounted on an electronic device, a notebook computer, a pen input computer, a mobile computer, an e-book reader, a mobile phone, a cordless handset, a pager, a handheld terminal, a portable Fax machines, portable copiers, portable printers, stereo headphones, camcorders, LCD TVs, portable vacuum cleaners, portable CDs, compact disks, electric shavers, transceivers, electronic notepads, calculators, memory cards, portable recorders, Radio, backup power, etc. Examples of other consumer goods include automobiles, electric vehicles, motors, lighting fixtures, toys, game consoles, load regulators, clocks, flashlights, cameras, and medical devices (pacemakers, hearing aids, and shoulder massagers). Moreover, it can be used as various military supplies and aviation supplies. Also, it can be combined with a solar cell.

Example

Hereinafter, the present invention will be described in further detail based on examples, but the present invention should not be construed as being limited thereto. In the following examples, "parts" and "%" indicating compositions are based on mass unless otherwise specified. In the present invention, "room temperature" refers to 25°C.

1. Synthesis of polymers and preparation of binder solutions or dispersions

The polymers S-1 to S-10, T-1 and T-2 shown in the following chemical formulas and Table 1 were synthesized as follows, and the binder solutions or dispersions S-1 to S-10, T-1 were prepared, respectively and T-2.

[Synthesis Example 1: Synthesis of Polymer S-1 (Preparation of Binder Dispersion Liquid S-1)]

27.0 g of 2-(2-methoxyethoxy)ethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) and dodecyl methacrylate (Tokyo Chemical Industry Co., Ltd.) were added to a 100 mL graduated cylinder. Ltd.) 9.0 g and a polymerization initiator V-601 (trade name, manufactured by FUJIFILM Wako Pure Chemical Corporation) 0.36 g were dissolved in 36 g of butyl butyrate to prepare a monomer solution.

To a 300 mL three-necked flask, 18 g of butyl butyrate was added, and the above-mentioned monomer solution was added dropwise at a stirring place at 80° C. over 2 hours. After the dropwise addition was completed, the temperature was raised to 90° C., stirred for 2 hours, and polymer S-1 (methacrylic polymer) was synthesized to obtain a dispersion liquid S-1 (concentration of a binder) composed of polymer S-1. 40% by mass). The average particle diameter of the binder S-1 in this dispersion liquid was 360 nm.

[Synthesis Examples 2 to 10: Synthesis of Polymers S-2 to S-10 (Preparation of Binder Solutions S-2 to S-10)]

In Synthesis Example 1, the compounds derived from the respective constituent components were used so that the polymers S-2 to S-10 had the compositions shown in the following chemical formulas and Table 1 (types and contents of constituent components), and other than that In the same manner as in Synthesis Example 1, polymers S-2 to S-6, S-8 and S-9 ((meth)acrylic polymers), and polymers S-7 and S-10 (ethylene polymers) were synthesized, respectively. base polymer), the binder solutions S-2 to S-10 (concentration: 40% by mass) composed of the respective polymers were obtained, respectively.

[Synthesis Example 11: Synthesis of Polymer T-1 (Preparation of Binder Dispersion Liquid T-1)]

60 g of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 39.3 g of N-methylpyrrolidone (NMP) were added to a 200 mL Erlenmeyer flask, and the A solution was obtained by stirring.

27.0 g of 4,4'-diaminodiphenyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) and 90 g of NMP were added to a 500-mL three-necked flask, and after stirring and dissolving, the above-mentioned 4,4'-(hexafluoroethylene) was added. isopropene) diphthalic anhydride in NMP so that the temperature in the reaction system does not exceed 60°C. After adding all this NMP solution, it stirred for 4 hours, and obtained the NMP solution (concentration 40 mass %) of a polymer.

Next, after adding 10 g of the NMP solution of the polymer and 30 g of NMP to a 500 mL three-necked eggplant-shaped flask and stirring, 316 g of butyl butyrate was added dropwise over 1 hour. The obtained dispersion liquid was transferred to a 1 L separatory funnel, washed three times with 250 g of water, and then dried with sodium sulfate.

Thus, the polymer T-1 (polyimide) was synthesized, and the binder dispersion liquid T-1 (concentration 1.3 mass %) consisting of the polymer T-1 was obtained.

The average particle diameter of the binder T-1 in this dispersion liquid was 530 nm.

[Synthesis Example 12: Synthesis of Polymer T-2 (Preparation of Binder Solution T-2)]

In Synthesis Example 1, the compounds into which the respective constituent components were introduced were used so that the polymer T-2 had the composition shown in the following chemical formula and Table 1 (types and contents of constituent components), and the same The polymer T-2 (acrylic polymer) was synthesized in the same manner, and the binder solution T-2 (concentration 40 mass %) consisting of the polymer T-2 was obtained.

The polymers S-1 to S-10, T-1 and T-2 are shown below.

The numbers at the lower right of each constituent component represent the content (mol%) in the polymer.

[Chemical formula 3]

[Chemical formula 4]

The composition, SP value, mass-average molecular weight, SP value of each constituent component, and average particle size of the binder of the synthesized polymers, and the form (solution or dispersion) of the binder in the composition described later shown in Table 1. The SP value of the polymer and each constituent component, the mass-average molecular weight of the polymer, and the average particle diameter of the binder are measured or calculated by the methods described above. When two kinds of components corresponding to specific constituent components are contained, it is divided into two paragraphs and described. The morphology of the adhesive was visually discriminated, but the adhesive marked as "dissolved" in the table satisfies the solubility based on the above solubility measurement.

<Abbreviation of table>

In the table, "-" in the column of constituent components means that there is no corresponding constituent.

The unit of SP value of each component shown below is MPa ^1/2 .

-Composition M1-

The structural component M1 represents other structural components such as a structural component whose SP value is less than 19.0 MPa ^1/2 .

LMA: Dodecyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

LA: Lauryl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

6FDA: 4,4'-(hexafluoroisopropene)diphthalic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.)

DAE: 4,4'-diaminodiphenyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

EtHexA: 2-ethylhexyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

-Constituent M2-

The structural component M2 represents a structural component derived from a (meth)acrylic monomer or a vinyl monomer having an SP value of 19.0 MPa ^1/2 or more.

DGMEM: 2-(2-methoxyethoxy)ethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

AN: Acrylonitrile (manufactured by FUJIFILM Wako Pure Chemical Corporation)

VP: Vinylpyridine (manufactured by Tokyo Chemical Industry Co., Ltd.)

OXE-30: (3-ethyloxetan-3-yl)methylmethacrylate (manufactured by OSAKA ORGANIC CHEMICALINDUSTRY LTD.)

THFA: Tetrahydrofurfuryl acrylate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

HEM: 2-hydroxyethyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

HEA: 2-hydroxyethyl acrylate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

St: Styrene (manufactured by FUJIFILM Wako Pure Chemical Corporation)

BA: Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

cHMA: cyclohexyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

2. Preparation of Active Substances

(1) As the positive electrode active material, the following LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NMC) was prepared.

NMC1: NMC with a specific surface area of 13 m ² /g and an average particle size of 0.3 μm (manufactured by TOYOSHIMA MFG Co,. Ltd.)

NMC2: NMC with a specific surface area of 4 m ² /g and an average particle size of 1.0 μm (manufactured by Aldrich, CO.LTD.)

(2) The following Si was prepared as the negative electrode active material.

Si1: Si with a specific surface area of 23 m ² /g and an average particle size of 0.1 μm (manufactured by Aldrich, CO.LTD.)

Si2: Si with a specific surface area of 2 m ² /g and an average particle size of 2.8 μm (manufactured by Alfa Aesar)

3. Synthesis of Sulfide-Based Inorganic Solid Electrolytes

[Synthesis Example A]

Sulfide-based inorganic solid electrolytes refer to T.Ohtomo, A.Hayashi, M.Tatsumisago, Y.Tsuchida, S.Hama, K.Kawamoto, Journal of Power Sources, 233, (2013), pp231-235 and A.Hayashi, The synthesis was carried out in the non-patent literature of S. Hama, H. Morimoto, M. Tatsumisago, T. Minami, Chem. Lett., (2001), pp872-873.

Specifically, 2.42 g of lithium sulfide (Li ₂ S, manufactured by Aldrich. Inc, purity > 99.98%) and 3.90 g of phosphorus pentasulfide (P ₂ S ₅ ) were weighed in a glove box under an argon atmosphere (dew point -70° C.). , manufactured by Aldrich. Inc, purity > 99%), put into an agate mortar, and mixed with an agate pestle for 5 minutes. The mixing ratio of Li ₂ S and P ₂ S ₅ was set to Li ₂ S:P ₂ S ₅ =75:25 in terms of molar ratio.

Next, 66 g of zirconia beads with a diameter of 5 mm were placed in a 45 mL container made of zirconia (manufactured by Fritsch Co., Ltd.), and the total amount of the mixture of lithium sulfide and phosphorus pentasulfide was placed, and the container was completely sealed under an argon atmosphere. A container was set in a planetary ball mill P-7 (trade name, manufactured by Fritsch Co., Ltd.), and mechanical grinding was performed at a temperature of 25° C. and a rotation speed of 720 rpm for 24 hours to obtain 6.20 g of yellow powder. The sulfide-based inorganic solid electrolyte (Li-PS-based glass, hereinafter, sometimes marked as LPS.). The average particle diameter of the Li-PS-based glass was 11 μm, and the specific surface area was 0.8 m ² /g.

[Example 1]

Each electrode composition shown in Table 2 was prepared as follows.

<Preparation of positive electrode composition>

Into a 45 mL container made of zirconia (manufactured by Fritsch Co., Ltd.), 60 g of zirconia beads with a diameter of 5 mm were placed, and 9.9 g of LPS synthesized in Synthesis Example A and 14 g (total amount) of butyl butyrate as a dispersion medium were placed . The container was installed in a planetary ball mill P-7 (trade name) manufactured by Fritsch Co., Ltd, and stirred at 25° C. for 30 minutes at a rotational speed of 200 rpm. Then, 25.2 g of the positive electrode active material shown in Table 2, 0.72 g of acetylene black (AB, average particle size: 2.3 μm, manufactured by Denka Company Limited) as a conductive auxiliary agent, and the binder shown in Table 2 were put into the container. 0.18 g of solution or dispersion (solid content mass), set the container in planetary ball mill P-7, and continue to mix for 30 minutes at a temperature of 25° C. and a rotation speed of 200 rpm to prepare positive electrode compositions (slurry) PK-1 to PK, respectively. -10 and PKc11.

<Preparation of negative electrode composition>

Into a 45 mL container made of zirconia (manufactured by Fritsch Co., Ltd.) 60 g of zirconia beads with a diameter of 5 mm were placed, and 8.7 g of LPS synthesized in Synthesis Example A and 0.1 of the binder solution or dispersion shown in Table 2 were placed g (solid content mass), and 20.8 g (total amount) of the dispersion medium shown in Table 2. The container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch Co., Ltd, and mixed at a temperature of 25° C. and a rotation speed of 300 rpm for 60 minutes. Then, 9.6 g of the negative electrode active material shown in Table 2 and 0.8 g of VGCF (average particle size: 0.8 μm, manufactured by SHOWA DENKO K.K.) as a conductive aid were put in, and the container was set in the planetary ball mill P-7 in the same manner, and the temperature was The negative electrode compositions (slurry) NK-1 to NK-10 and NKc21 to NKc23 were prepared by mixing at 25° C. and rotating speed of 100 rpm for 10 minutes, respectively.

<Abbreviation of table>

The composition content shows the content (mass %) with respect to the total amount of the composition, and the solid content shows the content (mass %) with respect to 100 mass % of the solid content of the composition.

NMC1 and NMC2: NMC prepared above

Si1 and Si2: Si prepared above

AB: Acetylene black (specific surface area is 62m ² /g)

VGCF: carbon nanotubes (specific surface area of 13m ² /g)

<Evaluation 1: Dispersion Stability Test>

For each of the prepared compositions, dispersion stability was evaluated as follows.

Each of the prepared compositions (slurry) was put into a glass test tube having a diameter of 10 mm and a height of 4 cm to a height of 4 cm, and was allowed to stand at 25° C. for 4 days. The solid content ratio of 1 cm was calculated from the slurry liquid level before and after standing. Specifically, immediately after standing, 1 cm of liquid was taken out from the slurry liquid surface downward, and was heated and dried at 120° C. in an aluminum cup for 2 hours. The mass of the solid content in the cup after that was measured, and each solid content before and after standing was calculated|required. The solid content ratio [WA/WB] of the thus obtained solid content amount WA after standing with respect to the solid content amount WB before standing was determined.

Depending on which of the following evaluation criteria the solid content ratio was included, the ease of precipitation (precipitation) of solid particles was evaluated as the dispersion stability of the solid electrolyte composition. In this test, the closer the solid content ratio is to 1.0, the more excellent the dispersion stability is shown, and the evaluation standard "D" or more is a pass level. The results are shown in Table 3.

In addition, the composition of the present invention has sufficient dispersibility as an electrode-forming material immediately after preparation.

-evaluation standard-

A: 0.9≤solid content ratio≤1.0

B: 0.8≤solid content ratio＜0.9

C: 0.7≤solid content ratio＜0.8

D: 0.6≤solid content ratio＜0.7

E: 0.5≤solid content ratio＜0.6

F: solid content ratio < 0.5

<Production of positive electrode sheet for all-solid-state secondary battery>

Using a bake-type applicator (trade name: SA-201), each positive electrode composition shown in the "electrode composition" column of Table 3 obtained above was coated on an aluminum foil with a thickness of 20 μm, and heated at 80° C. 1 hour, further heated at 110°C for 1 hour, and the positive electrode composition was dried (dispersed medium removed). Then, using a hot press, the dried positive electrode composition was pressurized at 25° C. (20 MPa, 1 minute) to produce positive electrode sheets for all-solid-state secondary batteries each having a positive electrode active material layer with a thickness of 75 μm. (In Table 3, it shows positive electrode sheet.) 101-106, 113-116, and c11.

<Production of negative electrode sheet for all-solid-state secondary battery>

Using a bake-type applicator (trade name: SA-201), each negative electrode composition shown in the "electrode composition" column of Table 3 obtained above was applied on a copper foil having a thickness of 20 μm, and the temperature was 80° C. Heating for 1 hour, further heating at 110° C. for 1 hour, and drying (removing the dispersion medium) of the negative electrode composition. Then, using a hot press, the dried negative electrode composition was pressurized at 25° C. (20 MPa, 1 minute) to produce negative electrode sheets for all-solid-state secondary batteries each having a negative electrode active material layer with a thickness of 60 μm. (Denoted as negative electrode sheet in Table 3.) 107 to 112, 117 to 120, and c21 to c23.

<Evaluation 2: Collector Adhesion>

Each of the produced sheets 101 to 120, c11, and c21 to c23 was cut out into a rectangle of width 3 cm x length 14 cm. Cylindrical mandrel sheets (product code 056, mandrel diameter 10 mm, manufactured by Allgood) were used, and were prepared in accordance with Japanese Industrial Standards (JIS) K5600-5-1 (and bending resistance (cylindrical mandrel: used Test of Type 2 Test Apparatus), the same test as International Standard (ISO) 1519.) The cut test piece was bent. In addition, in the test piece, the active material layer was provided on the side opposite to the mandrel (the current collector was provided on the mandrel side), and the width direction was parallel to the axis of the mandrel. The test was carried out by changing the diameter of the mandrel in the order of 32mm, 25mm, 19mm, 16mm, 12mm, 10mm, 6mm, 5mm, 3mm and 2mm, and the minimum value of the active material layer without peeling off from the current collector (aluminum foil or copper foil) was determined. diameter, and evaluate which of the following evaluation criteria the minimum diameter corresponds to.

In this test, the smaller the above-mentioned minimum diameter, the stronger the adhesion between the active material layer and the current collector, and the evaluation standard "D" or more is the pass level. The results are shown in Table 3.

-evaluation standard-

A: 2mm

B: 3mm or 5mm

C: 6mm or 10mm

D: 12mm or 16mm

E: 19mm or 25mm

F: 32mm

[table 3]

＜Manufacture of all-solid-state secondary battery＞

(Production of Positive Electrode Sheet for All-Solid-State Secondary Battery Equipped with Solid Electrolyte Layer)

Next, on the positive electrode active material layer of each positive electrode sheet for an all-solid-state secondary battery shown in the "electrode active material layer" column of Table 4, the solid electrolyte layer and the positive electrode active material layer were stacked on the positive electrode active material layer prepared as follows. The solid electrolyte sheet 201 for a solid-state secondary battery was pressurized (50 Mpa) at 25° C. using a press and transferred (laminated), and then further pressurized (600 Mpa) at 25° C., respectively. Positive electrode sheets for all-solid-state secondary batteries (film thickness of the positive electrode active material layer: 55 μm) having a solid electrolyte layer with a thickness of 30 μm were obtained 101 to 106 , 113 to 116 , and c11 .

<Preparation of negative electrode sheet for all-solid-state secondary battery provided with solid electrolyte layer>

Next, on the negative electrode active material layer of each negative electrode sheet for an all-solid-state secondary battery shown in the column of "electrode active material layer" in Table 4, the solid electrolyte layer and the negative electrode active material layer were laminated on the negative electrode active material layer prepared as follows. The solid electrolyte sheet 201 for a solid-state secondary battery was pressurized (50 Mpa) at 25° C. using a press and transferred (laminated), and then further pressurized (600 Mpa) at 25° C., respectively. Negative electrode sheets for all-solid-state secondary batteries (film thickness of the negative electrode active material layer: 42 μm) 107 to 112, 117 to 120, and c21 to c23 having a solid electrolyte layer with a film thickness of 30 μm were obtained.

The solid electrolyte sheet 201 for an all-solid-state secondary battery for manufacturing an all-solid-state secondary battery was produced as follows.

(Preparation of Composition 201 Containing Inorganic Solid Electrolyte)

60 g of zirconia beads having a diameter of 5 mm were placed in a 45 mL container made of zirconia (manufactured by Fritsch Co., Ltd.), and 8.43 g of LPS synthesized in the above Synthesis Example A and 0.17 g of KYNAR FLEX 2500-20 in terms of solid mass were placed (trade name, PVdF-HFP: polyvinylidene fluoride hexafluoropropylene copolymer, manufactured by ARKEMA) and 16 g of butyl butyrate as a dispersion medium. Then, the container was installed in a planetary ball mill P-7 (trade name) manufactured by Fritsch Co., Ltd. The composition (slurry) 201 containing an inorganic solid electrolyte was prepared by mixing at a temperature of 25° C. and a rotation speed of 150 rpm for 10 minutes.

(Production of solid electrolyte sheet 201 for all-solid-state secondary battery)

Using a bake-type applicator (trade name: SA-201, manufactured by TESTER SANGYO CO,. LTD.), the inorganic solid electrolyte-containing composition 201 prepared above was applied on an aluminum foil with a thickness of 20 μm, at 80° C. Heat for 2 hours, and dry (remove the dispersion medium) the composition containing the inorganic solid electrolyte. Then, the dried inorganic solid electrolyte-containing composition was heated and pressurized for 10 seconds at a temperature of 120° C. and a pressure of 40 MPa using a hot press, and solid electrolyte sheets for all-solid-state secondary batteries were produced, respectively. 201. The film thickness of the solid electrolyte layer was 48 μm.

(Manufacture of all-solid-state secondary batteries for evaluation of positive electrode sheets for all-solid-state secondary batteries No. 101 to 106, 113 to 116, and c11)

All-solid-state secondary battery No. 101 having the layer structure shown in FIG. 1 was produced as follows.

The positive electrode sheet No. 101 for an all-solid-state secondary battery provided with the solid electrolyte layer obtained above (aluminum foil from which the solid electrolyte-containing sheet has been peeled off) was cut into a disk shape with a diameter of 14.5 mm, as shown in FIG. 2 . It was introduced into a stainless steel 2032 type coin cell battery case 11 assembled with spacers and gaskets (not shown in FIG. 2 ). Next, on the solid electrolyte layer, a disk-shaped lithium foil having a diameter of 15 mm was laminated. After the stainless steel foil was further laminated thereon, the 2032-type coin-type battery case 11 was riveted, thereby manufacturing the (button-type) all-solid-state secondary battery (half cell) 13 of No. 101 shown in FIG. 2 . The positive electrode sheet for all-solid-state secondary battery No. 101 produced in this way has a layer structure as shown in FIG. 1 . ).

In the production of the above-mentioned all-solid-state secondary battery No. 101, the sheet No. 1 shown in the "electrode active material layer" column of Table 4 was used instead of the positive electrode sheet No. 101 for an all-solid-state secondary battery having a solid electrolyte layer. Except for the positive electrode sheet for all-solid-state secondary batteries having a solid electrolyte layer shown, in the same manner as the manufacture of all-solid-state secondary battery No. 101, positive electrode sheets for all-solid-state secondary batteries No. 102 were produced, respectively. -106, 113 to 116, and c11 All-solid-state secondary batteries (half cells) for evaluation No. 102 to 106, 113 to 116, and c101.

(Manufacture of all-solid-state secondary batteries for evaluation of negative electrode sheets for all-solid-state secondary batteries No. 107-112, 117-120, and c21-c23)

All-solid-state secondary battery No. 107 having the layer structure shown in FIG. 1 was produced as follows.

Each negative electrode sheet No. 107 for an all-solid-state secondary battery having the solid electrolyte obtained above (aluminum foil from which the solid electrolyte-containing sheet has been peeled off) was cut into a disk shape having a diameter of 14.5 mm, and was shown in FIG. 2 . It was introduced into a stainless steel 2032 type coin cell battery case 11 assembled with spacers and gaskets (not shown in FIG. 2 ). Next, a positive electrode sheet (positive electrode active material layer) punched out with a diameter of 14.0 mm from the positive electrode sheet CS for an all-solid-state secondary battery produced below was laminated on the solid electrolyte layer. A stainless steel foil (positive electrode current collector) was further laminated thereon to form a laminated body 12 for an all-solid-state secondary battery (comprised of stainless steel foil-aluminum foil-positive electrode active material layer-solid electrolyte layer-negative electrode active material layer-copper foil). laminate). Then, by caulking the 2032-type button case 11, the all-solid-state secondary battery (full battery) No.107 for evaluation of the negative electrode sheet No.107 for all-solid-state secondary batteries shown in FIG. 2 was manufactured.

The positive electrode sheet CS for an all-solid-state secondary battery used for manufacturing the all-solid-state secondary battery No. 107 was prepared as follows.

(Preparation of positive electrode composition)

180 zirconia beads with a diameter of 5 mm were placed in a 45 mL container made of zirconia (manufactured by Fritsch Co., Ltd.), and 2.7 g of LPS synthesized in Synthesis Example A above and 0.3 g of KYNAR FLEX 2500- 20 (trade name, PVdF-HFP: polyvinylidene fluoride hexafluoropropylene copolymer, manufactured by ARKEMA) and 22 g of butyl butyrate. The container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch Co., Ltd, and stirred at 25° C. for 60 minutes at a rotational speed of 300 rpm. Then, 7.0 g of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NMC, specific surface area 13 m ² /g, average particle diameter 0.3 μm) was put in as a positive electrode active material, and the container was installed on the planet in the same manner. In the ball mill P-7, mixing was continued for 5 minutes at 25° C. at a rotational speed of 100 rpm to prepare positive electrode compositions CS, respectively.

(Production of positive electrode sheet CS for all-solid-state secondary battery)

The positive electrode composition CS obtained above was applied on an aluminum foil (positive electrode current collector) with a thickness of 20 μm using a bake-type applicator (trade name: SA-201, manufactured by TESTER SANGYO CO,. LTD.), at 100 μm. The positive electrode composition CS was dried (removal of the dispersion medium) by heating at °C for 2 hours. Then, using a hot press, the dried positive electrode composition was pressurized at 25°C (10 MPa, 1 minute) to produce a positive electrode sheet CS for an all-solid-state secondary battery having a positive electrode active material layer with a thickness of 75 μm.

In the production of the above-mentioned all-solid-state secondary battery No. 107, the sheet No. 1 shown in the "electrode active material layer" column of Table 4 was used instead of the negative electrode sheet No. 107 for an all-solid-state secondary battery having a solid electrolyte layer. Except for the negative electrode sheet for all-solid-state secondary batteries having a solid electrolyte layer shown, in the same manner as the manufacture of all-solid-state secondary battery No.107, negative electrode sheets for all-solid-state secondary batteries No. 108 were produced, respectively. -112, 117-120, and c21-c23 all-solid-state secondary battery (full battery) No. 108-112, 117-120, and c201-c203 for evaluation.

<Evaluation 3: Cycle characteristic test under high-speed charge-discharge conditions>

For each of the manufactured all-solid-state secondary batteries for evaluation, the discharge capacity retention rate was measured with a charge-discharge evaluation apparatus TOSCAT-3000 (trade name, manufactured by TOYO SYSTEM Co., Ltd.).

Specifically, each all-solid-state secondary battery for evaluation was charged in an environment of 25° C. until the current density reached 0.1 mA/cm ² and the battery voltage reached 3.6 V. Then, discharge was performed until the current density reached 0.1 mA/cm ² and the battery voltage reached 2.5 V. One charge and one discharge were regarded as one charge-discharge cycle, and three cycles were repeated under the same conditions to initialize. Next, high-speed charging was performed at a current density of 1.0 mA/cm ² until the battery voltage reached 3.6 V. Then, high-speed discharge was performed at a current density of 1.0 mA/cm ² until the battery voltage reached 2.5 V. One high-rate charge and one high-rate discharge were regarded as one high-rate charge-discharge cycle, and high-rate charge and discharge were repeated under the same conditions. The discharge capacity of each all-solid-state secondary battery for evaluation was measured using a charge-discharge evaluation apparatus: TOSCAT-3000 (trade name) every time a high-speed charge-discharge cycle was performed.

The high-speed charge-discharge cycle when the discharge capacity retention ratio (discharge capacity relative to the initial discharge capacity) reaches 80%, assuming that the discharge capacity (initial discharge capacity) of the high-speed charge and discharge in the first cycle after initialization is 100% The cycle characteristics were evaluated according to which of the following evaluation criteria was included.

In this test, the evaluation criteria "D" or higher are acceptable criteria, and the higher the evaluation criteria, the more excellent the cycle characteristics, and the initial battery performance can be maintained even after repeated high-speed charge and discharge (even for long-term use). The results are shown in Table 4. The all-solid-state secondary batteries c101 and c201 are included in the evaluation criterion "E", and the above-mentioned high-speed charge-discharge cycle numbers are 210 cycles and 106 cycles, respectively.

In addition, in the all-solid-state secondary battery for evaluation of the present invention, the discharge capacity in the first high-speed charge-discharge cycle showed a value sufficient to function as an all-solid-state secondary battery. In addition, the all-solid-state secondary battery for evaluation of the present invention maintains excellent cycle characteristics even when normal charge-discharge cycles are repeated under the same conditions as the above-mentioned initialization, instead of the above-mentioned high-speed charge and discharge.

-Evaluation Criteria (Half Cell)-

A: More than 600 cycles

B: More than 500 cycles and less than 600 cycles

C: 400 cycles or more and less than 500 cycles

D: 300 cycles or more and less than 400 cycles

E: More than 200 cycles and less than 300 cycles

F: less than 200 cycles

-Evaluation criteria (full battery)-

A: More than 500 cycles

B: More than 400 cycles and less than 500 cycles

C: More than 300 cycles and less than 400 cycles

D: 200 cycles or more and less than 300 cycles

E: More than 100 cycles and less than 200 cycles

F: less than 100 cycles

[Table 4]

From the results shown in Tables 3 and 4, the following is understood.

The electrode compositions shown in Comparative Examples PKc11 and NKc21 to NKc23, which did not contain the sulfide-based inorganic solid electrolyte in combination with the active material and the polymer binder specified in the present invention, had poor dispersion stability. The sheets c11 and c21 to c23 produced using these compositions had poor adhesion to the current collector, and the discharge capacities of the all-solid-state secondary batteries c101 and c201 to c203 were significantly reduced due to high-speed charge and discharge.

On the other hand, as shown in PK-1 to PK-10 and NK-1 to NK-10 of the present invention, the sulfide-based inorganic solid electrolyte is combined with the active material and polymer binder specified in the present invention. Even if the contained electrode composition contains an active material with a large specific surface area, re-aggregation and precipitation over time can be suppressed, and sufficient dispersibility can be maintained even after 4 days have elapsed. By using these electrode compositions for forming an active material layer of an all-solid-state secondary battery, the current collector adhesion of the electrode sheet for an all-solid-state secondary battery can be enhanced, and the decrease in discharge capacity can be suppressed even during high-speed charge and discharge. It is possible to realize an all-solid-state secondary battery exhibiting excellent cycle characteristics. In an electrode composition containing an active material with a large specific surface area, the polymer binder is considered to be adsorbed to the active material, or even to the sulfide-based inorganic solid electrolyte, to exert this effect.

The present invention has been described along with the embodiments thereof, but unless otherwise specified, the present invention is not limited in any details of the description, and it is considered that the invention does not deviate from the idea and scope of the invention shown in the claims. should be interpreted broadly.

This application claims priority based on Japanese Patent Application No. 2020-055342 filed in Japanese Patent Application No. 2020-055342 filed in Japan on March 26, 2020, the contents of which are incorporated herein by reference as a part of the description in this specification.

Symbol Description

1- Negative current collector, 2- Negative electrode active material layer, 3- Solid electrolyte layer, 4- Positive electrode active material layer, 5- Positive electrode current collector, 6- Working part, 10- All-solid-state secondary battery, 11-2032 Type button battery case, 12-stack for all-solid-state secondary battery, 13-button-type all-solid-state secondary battery.

Claims (11)

1. An electrode composition for an all-solid-state secondary battery, comprising:

a sulfide-based inorganic solid electrolyte having ion conductivity of a metal belonging to group 1 or group 2 of the periodic table,

A polymer binder,

Active substance and

a dispersion medium for dispersing the components of the ink,

wherein,

the active substance has a particle size of 10m ² A specific surface area of at least g,

the polymer forming the polymer binder had an SP value of 19.0MPa ^1/2 The above constituent components derived from a (meth) acrylic monomer or a vinyl monomer.

2. The electrode composition of claim 1,

the polymeric binder is dissolved in the dispersion medium.

3. The electrode composition of claim 1 or 2,

the active material has silicon element as a constituent element.

4. The electrode composition of any one of claims 1 to 3,

the constituent component has a polar group or a heterocyclic group containing active hydrogen.

5. The electrode composition of any one of claims 1 to 4,

the constituent component has a structure represented by the following formula (M1) or formula (M2),

[ chemical formula 1]

In the formulae (M1) and (M2), R and R ¹ 、R ² And R ³ Represents a hydrogen atom or a substituent group,

l represents a linking group, L ¹ 、L ² And L ³ Represents a single bond or a linking group,

x represents-O-, -S-or-NR ^M -，R ^M Represents a hydrogen atom or a substituent，

Z represents-OH or-COOH.

6. The electrode composition of any one of claims 1 to 5,

the polymer forming the polymer binder is a (meth) acrylic polymer or a vinyl polymer.

7. An electrode composition according to any one of claims 1 to 6, which contains a conductive aid.

8. An electrode sheet for an all-solid secondary battery, having a layer composed of the electrode composition according to any one of claims 1 to 7 on a surface of a current collector.

9. An all-solid-state secondary battery comprising a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer in this order,

at least one of the positive electrode active material layer and the negative electrode active material layer is composed of the electrode composition according to any one of claims 1 to 7.

10. A method for manufacturing an electrode sheet for an all-solid-state secondary battery,

an electrode composition according to any one of claims 1 to 7 as a film on the surface of a current collector.

11. A method of manufacturing an all-solid-state secondary battery, by the manufacturing method according to claim 10.

Images